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Python3 sqi 2 png converter
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#!/usr/bin/env python | |
# $URL$ | |
# $Rev$ | |
# png.py - PNG encoder/decoder in pure Python | |
# | |
# Copyright (C) 2006 Johann C. Rocholl <johann@browsershots.org> | |
# Portions Copyright (C) 2009 David Jones <drj@pobox.com> | |
# And probably portions Copyright (C) 2006 Nicko van Someren <nicko@nicko.org> | |
# | |
# Original concept by Johann C. Rocholl. | |
# | |
# LICENSE (The MIT License) | |
# | |
# Permission is hereby granted, free of charge, to any person | |
# obtaining a copy of this software and associated documentation files | |
# (the "Software"), to deal in the Software without restriction, | |
# including without limitation the rights to use, copy, modify, merge, | |
# publish, distribute, sublicense, and/or sell copies of the Software, | |
# and to permit persons to whom the Software is furnished to do so, | |
# subject to the following conditions: | |
# | |
# The above copyright notice and this permission notice shall be | |
# included in all copies or substantial portions of the Software. | |
# | |
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, | |
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF | |
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND | |
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS | |
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN | |
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | |
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | |
# SOFTWARE. | |
# | |
# Changelog (recent first): | |
# 2009-03-11 David: interlaced bit depth < 8 (writing). | |
# 2009-03-10 David: interlaced bit depth < 8 (reading). | |
# 2009-03-04 David: Flat and Boxed pixel formats. | |
# 2009-02-26 David: Palette support (writing). | |
# 2009-02-23 David: Bit-depths < 8; better PNM support. | |
# 2006-06-17 Nicko: Reworked into a class, faster interlacing. | |
# 2006-06-17 Johann: Very simple prototype PNG decoder. | |
# 2006-06-17 Nicko: Test suite with various image generators. | |
# 2006-06-17 Nicko: Alpha-channel, grey-scale, 16-bit/plane support. | |
# 2006-06-15 Johann: Scanline iterator interface for large input files. | |
# 2006-06-09 Johann: Very simple prototype PNG encoder. | |
# Incorporated into Bangai-O Development Tools by drj on 2009-02-11 from | |
# http://trac.browsershots.org/browser/trunk/pypng/lib/png.py?rev=2885 | |
# Incorporated into pypng by drj on 2009-03-12 from | |
# //depot/prj/bangaio/master/code/png.py#67 | |
""" | |
Pure Python PNG Reader/Writer | |
This Python module implements support for PNG images (see PNG | |
specification at http://www.w3.org/TR/2003/REC-PNG-20031110/ ). It reads | |
and writes PNG files with all allowable bit depths (1/2/4/8/16/24/32/48/64 | |
bits per pixel) and colour combinations: greyscale (1/2/4/8/16 bit); RGB, | |
RGBA, LA (greyscale with alpha) with 8/16 bits per channel; colour mapped | |
images (1/2/4/8 bit). Adam7 interlacing is supported for reading and | |
writing. A number of optional chunks can be specified (when writing) | |
and understood (when reading): ``tRNS``, ``bKGD``, ``gAMA``. | |
For help, type ``import png; help(png)`` in your python interpreter. | |
A good place to start is the :class:`Reader` and :class:`Writer` classes. | |
Requires Python 2.3. Limited support is available for Python 2.2, but | |
not everything works. Best with Python 2.4 and higher. Installation is | |
trivial, but see the ``README.txt`` file (with the source distribution) | |
for details. | |
This file can also be used as a command-line utility to convert | |
`Netpbm <http://netpbm.sourceforge.net/>`_ PNM files to PNG, and the reverse conversion from PNG to | |
PNM. The interface is similar to that of the ``pnmtopng`` program from | |
Netpbm. Type ``python png.py --help`` at the shell prompt | |
for usage and a list of options. | |
A note on spelling and terminology | |
---------------------------------- | |
Generally British English spelling is used in the documentation. So | |
that's "greyscale" and "colour". This not only matches the author's | |
native language, it's also used by the PNG specification. | |
The major colour models supported by PNG (and hence by PyPNG) are: | |
greyscale, RGB, greyscale--alpha, RGB--alpha. These are sometimes | |
referred to using the abbreviations: L, RGB, LA, RGBA. In this case | |
each letter abbreviates a single channel: *L* is for Luminance or Luma or | |
Lightness which is the channel used in greyscale images; *R*, *G*, *B* stand | |
for Red, Green, Blue, the components of a colour image; *A* stands for | |
Alpha, the opacity channel (used for transparency effects, but higher | |
values are more opaque, so it makes sense to call it opacity). | |
A note on formats | |
----------------- | |
When getting pixel data out of this module (reading) and presenting | |
data to this module (writing) there are a number of ways the data could | |
be represented as a Python value. Generally this module uses one of | |
three formats called "flat row flat pixel", "boxed row flat pixel", and | |
"boxed row boxed pixel". Basically the concern is whether each pixel | |
and each row comes in its own little tuple (box), or not. | |
Consider an image that is 3 pixels wide by 2 pixels high, and each pixel | |
has RGB components: | |
Boxed row flat pixel:: | |
list([R,G,B, R,G,B, R,G,B], | |
[R,G,B, R,G,B, R,G,B]) | |
Each row appears as its own list, but the pixels are flattened so that | |
three values for one pixel simply follow the three values for the previous | |
pixel. This is the most common format used, because it provides a good | |
compromise between space and convenience. PyPNG regards itself as | |
at liberty to replace any sequence type with any sufficiently compatible | |
other sequence type; in practice each row is an array (from the array | |
module), and the outer list is sometimes an iterator rather than an | |
explicit list (so that streaming is possible). | |
Flat row flat pixel:: | |
[R,G,B, R,G,B, R,G,B, | |
R,G,B, R,G,B, R,G,B] | |
The entire image is one single giant sequence of colour values. | |
Generally an array will be used (to save space), not a list. | |
Boxed row boxed pixel:: | |
list([ (R,G,B), (R,G,B), (R,G,B) ], | |
[ (R,G,B), (R,G,B), (R,G,B) ]) | |
Each row appears in its own list, but each pixel also appears in its own | |
tuple. A serious memory burn in Python. | |
In all cases the top row comes first, and for each row the pixels are | |
ordered from left-to-right. Within a pixel the values appear in the | |
order, R-G-B-A (or L-A for greyscale--alpha). | |
There is a fourth format, mentioned because it is used internally, | |
is close to what lies inside a PNG file itself, and has some support | |
from the public API. This format is called packed. When packed, | |
each row is a sequence of bytes (integers from 0 to 255), just as | |
it is before PNG scanline filtering is applied. When the bit depth | |
is 8 this is essentially the same as boxed row flat pixel; when the | |
bit depth is less than 8, several pixels are packed into each byte; | |
when the bit depth is 16 (the only value more than 8 that is supported | |
by the PNG image format) each pixel value is decomposed into 2 bytes | |
(and `packed` is a misnomer). This format is used by the | |
:meth:`Writer.write_packed` method. It isn't usually a convenient | |
format, but may be just right if the source data for the PNG image | |
comes from something that uses a similar format (for example, 1-bit | |
BMPs, or another PNG file). | |
And now, my famous members | |
-------------------------- | |
""" | |
# http://www.python.org/doc/2.2.3/whatsnew/node5.html | |
__version__ = "$URL$ $Rev$" | |
from array import array | |
from functools import reduce | |
try: # See :pyver:old | |
import itertools | |
except: | |
pass | |
import math | |
# http://www.python.org/doc/2.4.4/lib/module-operator.html | |
import operator | |
import struct | |
import sys | |
import zlib | |
# http://www.python.org/doc/2.4.4/lib/module-warnings.html | |
import warnings | |
__all__ = ['Image', 'Reader', 'Writer', 'write_chunks', 'from_array'] | |
# The PNG signature. | |
# http://www.w3.org/TR/PNG/#5PNG-file-signature | |
_signature = struct.pack('8B', 137, 80, 78, 71, 13, 10, 26, 10) | |
_adam7 = ((0, 0, 8, 8), | |
(4, 0, 8, 8), | |
(0, 4, 4, 8), | |
(2, 0, 4, 4), | |
(0, 2, 2, 4), | |
(1, 0, 2, 2), | |
(0, 1, 1, 2)) | |
def group(s, n): | |
# See | |
# http://www.python.org/doc/2.6/library/functions.html#zip | |
return list(zip(*[iter(s)]*n)) | |
def isarray(x): | |
"""Same as ``isinstance(x, array)`` except on Python 2.2, where it | |
always returns ``False``. This helps PyPNG work on Python 2.2. | |
""" | |
try: | |
return isinstance(x, array) | |
except: | |
return False | |
try: # see :pyver:old | |
array.tostring | |
except: | |
def tostring(row): | |
l = len(row) | |
return struct.pack('%dB' % l, *row) | |
else: | |
def tostring(row): | |
"""Convert row of bytes to string. Expects `row` to be an | |
``array``. | |
""" | |
return row.tostring() | |
# Conditionally convert to bytes. Works on Python 2 and Python 3. | |
try: | |
bytes('', 'ascii') | |
def strtobytes(x): return bytes(x, 'iso8859-1') | |
def bytestostr(x): return str(x, 'iso8859-1') | |
except: | |
strtobytes = str | |
bytestostr = str | |
def interleave_planes(ipixels, apixels, ipsize, apsize): | |
""" | |
Interleave (colour) planes, e.g. RGB + A = RGBA. | |
Return an array of pixels consisting of the `ipsize` elements of data | |
from each pixel in `ipixels` followed by the `apsize` elements of data | |
from each pixel in `apixels`. Conventionally `ipixels` and | |
`apixels` are byte arrays so the sizes are bytes, but it actually | |
works with any arrays of the same type. The returned array is the | |
same type as the input arrays which should be the same type as each other. | |
""" | |
itotal = len(ipixels) | |
atotal = len(apixels) | |
newtotal = itotal + atotal | |
newpsize = ipsize + apsize | |
# Set up the output buffer | |
# See http://www.python.org/doc/2.4.4/lib/module-array.html#l2h-1356 | |
out = array(ipixels.typecode) | |
# It's annoying that there is no cheap way to set the array size :-( | |
out.extend(ipixels) | |
out.extend(apixels) | |
# Interleave in the pixel data | |
for i in range(ipsize): | |
out[i:newtotal:newpsize] = ipixels[i:itotal:ipsize] | |
for i in range(apsize): | |
out[i+ipsize:newtotal:newpsize] = apixels[i:atotal:apsize] | |
return out | |
def check_palette(palette): | |
"""Check a palette argument (to the :class:`Writer` class) for validity. | |
Returns the palette as a list if okay; raises an exception otherwise. | |
""" | |
# None is the default and is allowed. | |
if palette is None: | |
return None | |
p = list(palette) | |
if not (0 < len(p) <= 256): | |
raise ValueError("a palette must have between 1 and 256 entries") | |
seen_triple = False | |
for i,t in enumerate(p): | |
if len(t) not in (3,4): | |
raise ValueError( | |
"palette entry %d: entries must be 3- or 4-tuples." % i) | |
if len(t) == 3: | |
seen_triple = True | |
if seen_triple and len(t) == 4: | |
raise ValueError( | |
"palette entry %d: all 4-tuples must precede all 3-tuples" % i) | |
for x in t: | |
if int(x) != x or not(0 <= x <= 255): | |
raise ValueError( | |
"palette entry %d: values must be integer: 0 <= x <= 255" % i) | |
return p | |
class Error(Exception): | |
prefix = 'Error' | |
def __str__(self): | |
return self.prefix + ': ' + ' '.join(self.args) | |
class FormatError(Error): | |
"""Problem with input file format. In other words, PNG file does | |
not conform to the specification in some way and is invalid. | |
""" | |
prefix = 'FormatError' | |
class ChunkError(FormatError): | |
prefix = 'ChunkError' | |
class Writer: | |
""" | |
PNG encoder in pure Python. | |
""" | |
def __init__(self, width=None, height=None, | |
size=None, | |
greyscale=False, | |
alpha=False, | |
bitdepth=8, | |
palette=None, | |
transparent=None, | |
background=None, | |
gamma=None, | |
compression=None, | |
interlace=False, | |
bytes_per_sample=None, # deprecated | |
planes=None, | |
colormap=None, | |
maxval=None, | |
chunk_limit=2**20): | |
""" | |
Create a PNG encoder object. | |
Arguments: | |
width, height | |
Image size in pixels, as two separate arguments. | |
size | |
Image size (w,h) in pixels, as single argument. | |
greyscale | |
Input data is greyscale, not RGB. | |
alpha | |
Input data has alpha channel (RGBA or LA). | |
bitdepth | |
Bit depth: from 1 to 16. | |
palette | |
Create a palette for a colour mapped image (colour type 3). | |
transparent | |
Specify a transparent colour (create a ``tRNS`` chunk). | |
background | |
Specify a default background colour (create a ``bKGD`` chunk). | |
gamma | |
Specify a gamma value (create a ``gAMA`` chunk). | |
compression | |
zlib compression level (1-9). | |
interlace | |
Create an interlaced image. | |
chunk_limit | |
Write multiple ``IDAT`` chunks to save memory. | |
The image size (in pixels) can be specified either by using the | |
`width` and `height` arguments, or with the single `size` | |
argument. If `size` is used it should be a pair (*width*, | |
*height*). | |
`greyscale` and `alpha` are booleans that specify whether | |
an image is greyscale (or colour), and whether it has an | |
alpha channel (or not). | |
`bitdepth` specifies the bit depth of the source pixel values. | |
Each source pixel value must be an integer between 0 and | |
``2**bitdepth-1``. For example, 8-bit images have values | |
between 0 and 255. PNG only stores images with bit depths of | |
1,2,4,8, or 16. When `bitdepth` is not one of these values, | |
the next highest valid bit depth is selected, and an ``sBIT`` | |
(significant bits) chunk is generated that specifies the original | |
precision of the source image. In this case the supplied pixel | |
values will be rescaled to fit the range of the selected bit depth. | |
The details of which bit depth / colour model combinations the | |
PNG file format supports directly, are somewhat arcane | |
(refer to the PNG specification for full details). Briefly: | |
"small" bit depths (1,2,4) are only allowed with greyscale and | |
colour mapped images; colour mapped images cannot have bit depth | |
16. | |
For colour mapped images (in other words, when the `palette` | |
argument is specified) the `bitdepth` argument must match one of | |
the valid PNG bit depths: 1, 2, 4, or 8. (It is valid to have a | |
PNG image with a palette and an ``sBIT`` chunk, but the meaning | |
is slightly different; it would be awkward to press the | |
`bitdepth` argument into service for this.) | |
The `palette` option, when specified, causes a colour mapped image | |
to be created: the PNG colour type is set to 3; greyscale | |
must not be set; alpha must not be set; transparent must | |
not be set; the bit depth must be 1,2,4, or 8. When a colour | |
mapped image is created, the pixel values are palette indexes | |
and the `bitdepth` argument specifies the size of these indexes | |
(not the size of the colour values in the palette). | |
The palette argument value should be a sequence of 3- or | |
4-tuples. 3-tuples specify RGB palette entries; 4-tuples | |
specify RGBA palette entries. If both 4-tuples and 3-tuples | |
appear in the sequence then all the 4-tuples must come | |
before all the 3-tuples. A ``PLTE`` chunk is created; if there | |
are 4-tuples then a ``tRNS`` chunk is created as well. The | |
``PLTE`` chunk will contain all the RGB triples in the same | |
sequence; the ``tRNS`` chunk will contain the alpha channel for | |
all the 4-tuples, in the same sequence. Palette entries | |
are always 8-bit. | |
If specified, the `transparent` and `background` parameters must | |
be a tuple with three integer values for red, green, blue, or | |
a simple integer (or singleton tuple) for a greyscale image. | |
If specified, the `gamma` parameter must be a positive number | |
(generally, a float). A ``gAMA`` chunk will be created. Note that | |
this will not change the values of the pixels as they appear in | |
the PNG file, they are assumed to have already been converted | |
appropriately for the gamma specified. | |
The `compression` argument specifies the compression level | |
to be used by the ``zlib`` module. Higher values are likely | |
to compress better, but will be slower to compress. The | |
default for this argument is ``None``; this does not mean | |
no compression, rather it means that the default from the | |
``zlib`` module is used (which is generally acceptable). | |
If `interlace` is true then an interlaced image is created | |
(using PNG's so far only interace method, *Adam7*). This does not | |
affect how the pixels should be presented to the encoder, rather | |
it changes how they are arranged into the PNG file. On slow | |
connexions interlaced images can be partially decoded by the | |
browser to give a rough view of the image that is successively | |
refined as more image data appears. | |
.. note :: | |
Enabling the `interlace` option requires the entire image | |
to be processed in working memory. | |
`chunk_limit` is used to limit the amount of memory used whilst | |
compressing the image. In order to avoid using large amounts of | |
memory, multiple ``IDAT`` chunks may be created. | |
""" | |
# At the moment the `planes` argument is ignored; | |
# its purpose is to act as a dummy so that | |
# ``Writer(x, y, **info)`` works, where `info` is a dictionary | |
# returned by Reader.read and friends. | |
# Ditto for `colormap`. | |
# A couple of helper functions come first. Best skipped if you | |
# are reading through. | |
def isinteger(x): | |
try: | |
return int(x) == x | |
except: | |
return False | |
def check_color(c, which): | |
"""Checks that a colour argument for transparent or | |
background options is the right form. Also "corrects" bare | |
integers to 1-tuples. | |
""" | |
if c is None: | |
return c | |
if greyscale: | |
try: | |
l = len(c) | |
except TypeError: | |
c = (c,) | |
if len(c) != 1: | |
raise ValueError("%s for greyscale must be 1-tuple" % | |
which) | |
if not isinteger(c[0]): | |
raise ValueError( | |
"%s colour for greyscale must be integer" % | |
which) | |
else: | |
if not (len(c) == 3 and | |
isinteger(c[0]) and | |
isinteger(c[1]) and | |
isinteger(c[2])): | |
raise ValueError( | |
"%s colour must be a triple of integers" % | |
which) | |
return c | |
if size: | |
if len(size) != 2: | |
raise ValueError( | |
"size argument should be a pair (width, height)") | |
if width is not None and width != size[0]: | |
raise ValueError( | |
"size[0] (%r) and width (%r) should match when both are used." | |
% (size[0], width)) | |
if height is not None and height != size[1]: | |
raise ValueError( | |
"size[1] (%r) and height (%r) should match when both are used." | |
% (size[1], height)) | |
width,height = size | |
del size | |
if width <= 0 or height <= 0: | |
raise ValueError("width and height must be greater than zero") | |
if not isinteger(width) or not isinteger(height): | |
raise ValueError("width and height must be integers") | |
# http://www.w3.org/TR/PNG/#7Integers-and-byte-order | |
if width > 2**32-1 or height > 2**32-1: | |
raise ValueError("width and height cannot exceed 2**32-1") | |
if alpha and transparent is not None: | |
raise ValueError( | |
"transparent colour not allowed with alpha channel") | |
if bytes_per_sample is not None: | |
warnings.warn('please use bitdepth instead of bytes_per_sample', | |
DeprecationWarning) | |
if bytes_per_sample not in (0.125, 0.25, 0.5, 1, 2): | |
raise ValueError( | |
"bytes per sample must be .125, .25, .5, 1, or 2") | |
bitdepth = int(8*bytes_per_sample) | |
del bytes_per_sample | |
if not isinteger(bitdepth) or bitdepth < 1 or 16 < bitdepth: | |
raise ValueError("bitdepth (%r) must be a postive integer <= 16" % | |
bitdepth) | |
self.rescale = None | |
if palette: | |
if bitdepth not in (1,2,4,8): | |
raise ValueError("with palette, bitdepth must be 1, 2, 4, or 8") | |
if transparent is not None: | |
raise ValueError("transparent and palette not compatible") | |
if alpha: | |
raise ValueError("alpha and palette not compatible") | |
if greyscale: | |
raise ValueError("greyscale and palette not compatible") | |
else: | |
# No palette, check for sBIT chunk generation. | |
if alpha or not greyscale: | |
if bitdepth not in (8,16): | |
targetbitdepth = (8,16)[bitdepth > 8] | |
self.rescale = (bitdepth, targetbitdepth) | |
bitdepth = targetbitdepth | |
del targetbitdepth | |
else: | |
assert greyscale | |
assert not alpha | |
if bitdepth not in (1,2,4,8,16): | |
if bitdepth > 8: | |
targetbitdepth = 16 | |
elif bitdepth == 3: | |
targetbitdepth = 4 | |
else: | |
assert bitdepth in (5,6,7) | |
targetbitdepth = 8 | |
self.rescale = (bitdepth, targetbitdepth) | |
bitdepth = targetbitdepth | |
del targetbitdepth | |
if bitdepth < 8 and (alpha or not greyscale and not palette): | |
raise ValueError( | |
"bitdepth < 8 only permitted with greyscale or palette") | |
if bitdepth > 8 and palette: | |
raise ValueError( | |
"bit depth must be 8 or less for images with palette") | |
transparent = check_color(transparent, 'transparent') | |
background = check_color(background, 'background') | |
# It's important that the true boolean values (greyscale, alpha, | |
# colormap, interlace) are converted to bool because Iverson's | |
# convention is relied upon later on. | |
self.width = width | |
self.height = height | |
self.transparent = transparent | |
self.background = background | |
self.gamma = gamma | |
self.greyscale = bool(greyscale) | |
self.alpha = bool(alpha) | |
self.colormap = bool(palette) | |
self.bitdepth = int(bitdepth) | |
self.compression = compression | |
self.chunk_limit = chunk_limit | |
self.interlace = bool(interlace) | |
self.palette = check_palette(palette) | |
self.color_type = 4*self.alpha + 2*(not greyscale) + 1*self.colormap | |
assert self.color_type in (0,2,3,4,6) | |
self.color_planes = (3,1)[self.greyscale or self.colormap] | |
self.planes = self.color_planes + self.alpha | |
# :todo: fix for bitdepth < 8 | |
self.psize = (self.bitdepth/8) * self.planes | |
def make_palette(self): | |
"""Create the byte sequences for a ``PLTE`` and if necessary a | |
``tRNS`` chunk. Returned as a pair (*p*, *t*). *t* will be | |
``None`` if no ``tRNS`` chunk is necessary. | |
""" | |
p = array('B') | |
t = array('B') | |
for x in self.palette: | |
p.extend(x[0:3]) | |
if len(x) > 3: | |
t.append(x[3]) | |
p = tostring(p) | |
t = tostring(t) | |
if t: | |
return p,t | |
return p,None | |
def write(self, outfile, rows): | |
"""Write a PNG image to the output file. `rows` should be | |
an iterable that yields each row in boxed row flat pixel format. | |
The rows should be the rows of the original image, so there | |
should be ``self.height`` rows of ``self.width * self.planes`` values. | |
If `interlace` is specified (when creating the instance), then | |
an interlaced PNG file will be written. Supply the rows in the | |
normal image order; the interlacing is carried out internally. | |
.. note :: | |
Interlacing will require the entire image to be in working memory. | |
""" | |
if self.interlace: | |
fmt = 'BH'[self.bitdepth > 8] | |
a = array(fmt, itertools.chain(*rows)) | |
return self.write_array(outfile, a) | |
else: | |
nrows = self.write_passes(outfile, rows) | |
if nrows != self.height: | |
raise ValueError( | |
"rows supplied (%d) does not match height (%d)" % | |
(nrows, self.height)) | |
def write_passes(self, outfile, rows, packed=False): | |
""" | |
Write a PNG image to the output file. | |
Most users are expected to find the :meth:`write` or | |
:meth:`write_array` method more convenient. | |
The rows should be given to this method in the order that | |
they appear in the output file. For straightlaced images, | |
this is the usual top to bottom ordering, but for interlaced | |
images the rows should have already been interlaced before | |
passing them to this function. | |
`rows` should be an iterable that yields each row. When | |
`packed` is ``False`` the rows should be in boxed row flat pixel | |
format; when `packed` is ``True`` each row should be a packed | |
sequence of bytes. | |
""" | |
# http://www.w3.org/TR/PNG/#5PNG-file-signature | |
outfile.write(_signature) | |
# http://www.w3.org/TR/PNG/#11IHDR | |
write_chunk(outfile, 'IHDR', | |
struct.pack("!2I5B", self.width, self.height, | |
self.bitdepth, self.color_type, | |
0, 0, self.interlace)) | |
# See :chunk:order | |
# http://www.w3.org/TR/PNG/#11gAMA | |
if self.gamma is not None: | |
write_chunk(outfile, 'gAMA', | |
struct.pack("!L", int(round(self.gamma*1e5)))) | |
# See :chunk:order | |
# http://www.w3.org/TR/PNG/#11sBIT | |
if self.rescale: | |
write_chunk(outfile, 'sBIT', | |
struct.pack('%dB' % self.planes, | |
*[self.rescale[0]]*self.planes)) | |
# :chunk:order: Without a palette (PLTE chunk), ordering is | |
# relatively relaxed. With one, gAMA chunk must precede PLTE | |
# chunk which must precede tRNS and bKGD. | |
# See http://www.w3.org/TR/PNG/#5ChunkOrdering | |
if self.palette: | |
p,t = self.make_palette() | |
write_chunk(outfile, 'PLTE', p) | |
if t: | |
# tRNS chunk is optional. Only needed if palette entries | |
# have alpha. | |
write_chunk(outfile, 'tRNS', t) | |
# http://www.w3.org/TR/PNG/#11tRNS | |
if self.transparent is not None: | |
if self.greyscale: | |
write_chunk(outfile, 'tRNS', | |
struct.pack("!1H", *self.transparent)) | |
else: | |
write_chunk(outfile, 'tRNS', | |
struct.pack("!3H", *self.transparent)) | |
# http://www.w3.org/TR/PNG/#11bKGD | |
if self.background is not None: | |
if self.greyscale: | |
write_chunk(outfile, 'bKGD', | |
struct.pack("!1H", *self.background)) | |
else: | |
write_chunk(outfile, 'bKGD', | |
struct.pack("!3H", *self.background)) | |
# http://www.w3.org/TR/PNG/#11IDAT | |
if self.compression is not None: | |
compressor = zlib.compressobj(self.compression) | |
else: | |
compressor = zlib.compressobj() | |
# Choose an extend function based on the bitdepth. The extend | |
# function packs/decomposes the pixel values into bytes and | |
# stuffs them onto the data array. | |
data = array('B') | |
if self.bitdepth == 8 or packed: | |
extend = data.extend | |
elif self.bitdepth == 16: | |
# Decompose into bytes | |
def extend(sl): | |
fmt = '!%dH' % len(sl) | |
data.extend(array('B', struct.pack(fmt, *sl))) | |
else: | |
# Pack into bytes | |
assert self.bitdepth < 8 | |
# samples per byte | |
spb = int(8/self.bitdepth) | |
def extend(sl): | |
a = array('B', sl) | |
# Adding padding bytes so we can group into a whole | |
# number of spb-tuples. | |
l = float(len(a)) | |
extra = math.ceil(l / float(spb))*spb - l | |
a.extend([0]*int(extra)) | |
# Pack into bytes | |
l = group(a, spb) | |
l = [reduce(lambda x,y: | |
(x << self.bitdepth) + y, e) for e in l] | |
data.extend(l) | |
if self.rescale: | |
oldextend = extend | |
factor = \ | |
float(2**self.rescale[1]-1) / float(2**self.rescale[0]-1) | |
def extend(sl): | |
oldextend([int(round(factor*x)) for x in sl]) | |
# Build the first row, testing mostly to see if we need to | |
# changed the extend function to cope with NumPy integer types | |
# (they cause our ordinary definition of extend to fail, so we | |
# wrap it). See | |
# http://code.google.com/p/pypng/issues/detail?id=44 | |
enumrows = enumerate(rows) | |
del rows | |
# First row's filter type. | |
data.append(0) | |
# :todo: Certain exceptions in the call to ``.next()`` or the | |
# following try would indicate no row data supplied. | |
# Should catch. | |
i,row = next(enumrows) | |
try: | |
# If this fails... | |
extend(row) | |
except: | |
# ... try a version that converts the values to int first. | |
# Not only does this work for the (slightly broken) NumPy | |
# types, there are probably lots of other, unknown, "nearly" | |
# int types it works for. | |
def wrapmapint(f): | |
return lambda sl: f(list(map(int, sl))) | |
extend = wrapmapint(extend) | |
del wrapmapint | |
extend(row) | |
for i,row in enumrows: | |
# Add "None" filter type. Currently, it's essential that | |
# this filter type be used for every scanline as we do not | |
# mark the first row of a reduced pass image; that means we | |
# could accidentally compute the wrong filtered scanline if | |
# we used "up", "average", or "paeth" on such a line. | |
data.append(0) | |
extend(row) | |
if len(data) > self.chunk_limit: | |
compressed = compressor.compress(tostring(data)) | |
if len(compressed): | |
# print >> sys.stderr, len(data), len(compressed) | |
write_chunk(outfile, 'IDAT', compressed) | |
# Because of our very witty definition of ``extend``, | |
# above, we must re-use the same ``data`` object. Hence | |
# we use ``del`` to empty this one, rather than create a | |
# fresh one (which would be my natural FP instinct). | |
del data[:] | |
if len(data): | |
compressed = compressor.compress(tostring(data)) | |
else: | |
compressed = strtobytes('') | |
flushed = compressor.flush() | |
if len(compressed) or len(flushed): | |
# print >> sys.stderr, len(data), len(compressed), len(flushed) | |
write_chunk(outfile, 'IDAT', compressed + flushed) | |
# http://www.w3.org/TR/PNG/#11IEND | |
write_chunk(outfile, 'IEND') | |
return i+1 | |
def write_array(self, outfile, pixels): | |
""" | |
Write an array in flat row flat pixel format as a PNG file on | |
the output file. See also :meth:`write` method. | |
""" | |
if self.interlace: | |
self.write_passes(outfile, self.array_scanlines_interlace(pixels)) | |
else: | |
self.write_passes(outfile, self.array_scanlines(pixels)) | |
def write_packed(self, outfile, rows): | |
""" | |
Write PNG file to `outfile`. The pixel data comes from `rows` | |
which should be in boxed row packed format. Each row should be | |
a sequence of packed bytes. | |
Technically, this method does work for interlaced images but it | |
is best avoided. For interlaced images, the rows should be | |
presented in the order that they appear in the file. | |
This method should not be used when the source image bit depth | |
is not one naturally supported by PNG; the bit depth should be | |
1, 2, 4, 8, or 16. | |
""" | |
if self.rescale: | |
raise Error("write_packed method not suitable for bit depth %d" % | |
self.rescale[0]) | |
return self.write_passes(outfile, rows, packed=True) | |
def convert_pnm(self, infile, outfile): | |
""" | |
Convert a PNM file containing raw pixel data into a PNG file | |
with the parameters set in the writer object. Works for | |
(binary) PGM, PPM, and PAM formats. | |
""" | |
if self.interlace: | |
pixels = array('B') | |
pixels.fromfile(infile, | |
(self.bitdepth/8) * self.color_planes * | |
self.width * self.height) | |
self.write_passes(outfile, self.array_scanlines_interlace(pixels)) | |
else: | |
self.write_passes(outfile, self.file_scanlines(infile)) | |
def convert_ppm_and_pgm(self, ppmfile, pgmfile, outfile): | |
""" | |
Convert a PPM and PGM file containing raw pixel data into a | |
PNG outfile with the parameters set in the writer object. | |
""" | |
pixels = array('B') | |
pixels.fromfile(ppmfile, | |
(self.bitdepth/8) * self.color_planes * | |
self.width * self.height) | |
apixels = array('B') | |
apixels.fromfile(pgmfile, | |
(self.bitdepth/8) * | |
self.width * self.height) | |
pixels = interleave_planes(pixels, apixels, | |
(self.bitdepth/8) * self.color_planes, | |
(self.bitdepth/8)) | |
if self.interlace: | |
self.write_passes(outfile, self.array_scanlines_interlace(pixels)) | |
else: | |
self.write_passes(outfile, self.array_scanlines(pixels)) | |
def file_scanlines(self, infile): | |
""" | |
Generates boxed rows in flat pixel format, from the input file | |
`infile`. It assumes that the input file is in a "Netpbm-like" | |
binary format, and is positioned at the beginning of the first | |
pixel. The number of pixels to read is taken from the image | |
dimensions (`width`, `height`, `planes`) and the number of bytes | |
per value is implied by the image `bitdepth`. | |
""" | |
# Values per row | |
vpr = self.width * self.planes | |
row_bytes = vpr | |
if self.bitdepth > 8: | |
assert self.bitdepth == 16 | |
row_bytes *= 2 | |
fmt = '>%dH' % vpr | |
def line(): | |
return array('H', struct.unpack(fmt, infile.read(row_bytes))) | |
else: | |
def line(): | |
scanline = array('B', infile.read(row_bytes)) | |
return scanline | |
for y in range(self.height): | |
yield line() | |
def array_scanlines(self, pixels): | |
""" | |
Generates boxed rows (flat pixels) from flat rows (flat pixels) | |
in an array. | |
""" | |
# Values per row | |
vpr = self.width * self.planes | |
stop = 0 | |
for y in range(self.height): | |
start = stop | |
stop = start + vpr | |
yield pixels[start:stop] | |
def array_scanlines_interlace(self, pixels): | |
""" | |
Generator for interlaced scanlines from an array. `pixels` is | |
the full source image in flat row flat pixel format. The | |
generator yields each scanline of the reduced passes in turn, in | |
boxed row flat pixel format. | |
""" | |
# http://www.w3.org/TR/PNG/#8InterlaceMethods | |
# Array type. | |
fmt = 'BH'[self.bitdepth > 8] | |
# Value per row | |
vpr = self.width * self.planes | |
for xstart, ystart, xstep, ystep in _adam7: | |
if xstart >= self.width: | |
continue | |
# Pixels per row (of reduced image) | |
ppr = int(math.ceil((self.width-xstart)/float(xstep))) | |
# number of values in reduced image row. | |
row_len = ppr*self.planes | |
for y in range(ystart, self.height, ystep): | |
if xstep == 1: | |
offset = y * vpr | |
yield pixels[offset:offset+vpr] | |
else: | |
row = array(fmt) | |
# There's no easier way to set the length of an array | |
row.extend(pixels[0:row_len]) | |
offset = y * vpr + xstart * self.planes | |
end_offset = (y+1) * vpr | |
skip = self.planes * xstep | |
for i in range(self.planes): | |
row[i::self.planes] = \ | |
pixels[offset+i:end_offset:skip] | |
yield row | |
def write_chunk(outfile, tag, data=strtobytes('')): | |
""" | |
Write a PNG chunk to the output file, including length and | |
checksum. | |
""" | |
# http://www.w3.org/TR/PNG/#5Chunk-layout | |
outfile.write(struct.pack("!I", len(data))) | |
tag = strtobytes(tag) | |
outfile.write(tag) | |
outfile.write(data) | |
checksum = zlib.crc32(tag) | |
checksum = zlib.crc32(data, checksum) | |
checksum &= 2**32-1 | |
outfile.write(struct.pack("!I", checksum)) | |
def write_chunks(out, chunks): | |
"""Create a PNG file by writing out the chunks.""" | |
out.write(_signature) | |
for chunk in chunks: | |
write_chunk(out, *chunk) | |
def filter_scanline(type, line, fo, prev=None): | |
"""Apply a scanline filter to a scanline. `type` specifies the | |
filter type (0 to 4); `line` specifies the current (unfiltered) | |
scanline as a sequence of bytes; `prev` specifies the previous | |
(unfiltered) scanline as a sequence of bytes. `fo` specifies the | |
filter offset; normally this is size of a pixel in bytes (the number | |
of bytes per sample times the number of channels), but when this is | |
< 1 (for bit depths < 8) then the filter offset is 1. | |
""" | |
assert 0 <= type < 5 | |
# The output array. Which, pathetically, we extend one-byte at a | |
# time (fortunately this is linear). | |
out = array('B', [type]) | |
def sub(): | |
ai = -fo | |
for x in line: | |
if ai >= 0: | |
x = (x - line[ai]) & 0xff | |
out.append(x) | |
ai += 1 | |
def up(): | |
for i,x in enumerate(line): | |
x = (x - prev[i]) & 0xff | |
out.append(x) | |
def average(): | |
ai = -fo | |
for i,x in enumerate(line): | |
if ai >= 0: | |
x = (x - ((line[ai] + prev[i]) >> 1)) & 0xff | |
else: | |
x = (x - (prev[i] >> 1)) & 0xff | |
out.append(x) | |
ai += 1 | |
def paeth(): | |
# http://www.w3.org/TR/PNG/#9Filter-type-4-Paeth | |
ai = -fo # also used for ci | |
for i,x in enumerate(line): | |
a = 0 | |
b = prev[i] | |
c = 0 | |
if ai >= 0: | |
a = line[ai] | |
c = prev[ai] | |
p = a + b - c | |
pa = abs(p - a) | |
pb = abs(p - b) | |
pc = abs(p - c) | |
if pa <= pb and pa <= pc: Pr = a | |
elif pb <= pc: Pr = b | |
else: Pr = c | |
x = (x - Pr) & 0xff | |
out.append(x) | |
ai += 1 | |
if not prev: | |
# We're on the first line. Some of the filters can be reduced | |
# to simpler cases which makes handling the line "off the top" | |
# of the image simpler. "up" becomes "none"; "paeth" becomes | |
# "left" (non-trivial, but true). "average" needs to be handled | |
# specially. | |
if type == 2: # "up" | |
return line # type = 0 | |
elif type == 3: | |
prev = [0]*len(line) | |
elif type == 4: # "paeth" | |
type = 1 | |
if type == 0: | |
out.extend(line) | |
elif type == 1: | |
sub() | |
elif type == 2: | |
up() | |
elif type == 3: | |
average() | |
else: # type == 4 | |
paeth() | |
return out | |
def from_array(a, mode=None, info={}): | |
"""Create a PNG :class:`Image` object from a 2- or 3-dimensional array. | |
One application of this function is easy PIL-style saving: | |
``png.from_array(pixels, 'L').save('foo.png')``. | |
.. note : | |
The use of the term *3-dimensional* is for marketing purposes | |
only. It doesn't actually work. Please bear with us. Meanwhile | |
enjoy the complimentary snacks (on request) and please use a | |
2-dimensional array. | |
Unless they are specified using the *info* parameter, the PNG's | |
height and width are taken from the array size. For a 3 dimensional | |
array the first axis is the height; the second axis is the width; | |
and the third axis is the channel number. Thus an RGB image that is | |
16 pixels high and 8 wide will use an array that is 16x8x3. For 2 | |
dimensional arrays the first axis is the height, but the second axis | |
is ``width*channels``, so an RGB image that is 16 pixels high and 8 | |
wide will use a 2-dimensional array that is 16x24 (each row will be | |
8*3==24 sample values). | |
*mode* is a string that specifies the image colour format in a | |
PIL-style mode. It can be: | |
``'L'`` | |
greyscale (1 channel) | |
``'LA'`` | |
greyscale with alpha (2 channel) | |
``'RGB'`` | |
colour image (3 channel) | |
``'RGBA'`` | |
colour image with alpha (4 channel) | |
The mode string can also specify the bit depth (overriding how this | |
function normally derives the bit depth, see below). Appending | |
``';16'`` to the mode will cause the PNG to be 16 bits per channel; | |
any decimal from 1 to 16 can be used to specify the bit depth. | |
When a 2-dimensional array is used *mode* determines how many | |
channels the image has, and so allows the width to be derived from | |
the second array dimension. | |
The array is expected to be a ``numpy`` array, but it can be any | |
suitable Python sequence. For example, a list of lists can be used: | |
``png.from_array([[0, 255, 0], [255, 0, 255]], 'L')``. The exact | |
rules are: ``len(a)`` gives the first dimension, height; | |
``len(a[0])`` gives the second dimension; ``len(a[0][0])`` gives the | |
third dimension, unless an exception is raised in which case a | |
2-dimensional array is assumed. It's slightly more complicated than | |
that because an iterator of rows can be used, and it all still | |
works. Using an iterator allows data to be streamed efficiently. | |
The bit depth of the PNG is normally taken from the array element's | |
datatype (but if *mode* specifies a bitdepth then that is used | |
instead). The array element's datatype is determined in a way which | |
is supposed to work both for ``numpy`` arrays and for Python | |
``array.array`` objects. A 1 byte datatype will give a bit depth of | |
8, a 2 byte datatype will give a bit depth of 16. If the datatype | |
does not have an implicit size, for example it is a plain Python | |
list of lists, as above, then a default of 8 is used. | |
The *info* parameter is a dictionary that can be used to specify | |
metadata (in the same style as the arguments to the | |
:class:``png.Writer`` class). For this function the keys that are | |
useful are: | |
height | |
overrides the height derived from the array dimensions and allows | |
*a* to be an iterable. | |
width | |
overrides the width derived from the array dimensions. | |
bitdepth | |
overrides the bit depth derived from the element datatype (but | |
must match *mode* if that also specifies a bit depth). | |
Generally anything specified in the | |
*info* dictionary will override any implicit choices that this | |
function would otherwise make, but must match any explicit ones. | |
For example, if the *info* dictionary has a ``greyscale`` key then | |
this must be true when mode is ``'L'`` or ``'LA'`` and false when | |
mode is ``'RGB'`` or ``'RGBA'``. | |
""" | |
# We abuse the *info* parameter by modifying it. Take a copy here. | |
# (Also typechecks *info* to some extent). | |
info = dict(info) | |
# Syntax check mode string. | |
bitdepth = None | |
try: | |
mode = mode.split(';') | |
if len(mode) not in (1,2): | |
raise Error() | |
if mode[0] not in ('L', 'LA', 'RGB', 'RGBA'): | |
raise Error() | |
if len(mode) == 2: | |
try: | |
bitdepth = int(mode[1]) | |
except: | |
raise Error() | |
except Error: | |
raise Error("mode string should be 'RGB' or 'L;16' or similar.") | |
mode = mode[0] | |
# Get bitdepth from *mode* if possible. | |
if bitdepth: | |
if info.get('bitdepth') and bitdepth != info['bitdepth']: | |
raise Error("mode bitdepth (%d) should match info bitdepth (%d)." % | |
(bitdepth, info['bitdepth'])) | |
info['bitdepth'] = bitdepth | |
# Fill in and/or check entries in *info*. | |
# Dimensions. | |
if 'size' in info: | |
# Check width, height, size all match where used. | |
for dimension,axis in [('width', 0), ('height', 1)]: | |
if dimension in info: | |
if info[dimension] != info['size'][axis]: | |
raise Error( | |
"info[%r] shhould match info['size'][%r]." % | |
(dimension, axis)) | |
info['width'],info['height'] = info['size'] | |
if 'height' not in info: | |
try: | |
l = len(a) | |
except: | |
raise Error( | |
"len(a) does not work, supply info['height'] instead.") | |
info['height'] = l | |
# Colour format. | |
if 'greyscale' in info: | |
if bool(info['greyscale']) != ('L' in mode): | |
raise Error("info['greyscale'] should match mode.") | |
info['greyscale'] = 'L' in mode | |
if 'alpha' in info: | |
if bool(info['alpha']) != ('A' in mode): | |
raise Error("info['alpha'] should match mode.") | |
info['alpha'] = 'A' in mode | |
planes = len(mode) | |
if 'planes' in info: | |
if info['planes'] != planes: | |
raise Error("info['planes'] should match mode.") | |
# In order to work out whether we the array is 2D or 3D we need its | |
# first row, which requires that we take a copy of its iterator. | |
# We may also need the first row to derive width and bitdepth. | |
a,t = itertools.tee(a) | |
row = next(t) | |
del t | |
try: | |
row[0][0] | |
threed = True | |
testelement = row[0] | |
except: | |
threed = False | |
testelement = row | |
if 'width' not in info: | |
if threed: | |
width = len(row) | |
else: | |
width = len(row) // planes | |
info['width'] = width | |
# Not implemented yet | |
assert not threed | |
if 'bitdepth' not in info: | |
try: | |
dtype = testelement.dtype | |
# goto the "else:" clause. Sorry. | |
except: | |
try: | |
# Try a Python array.array. | |
bitdepth = 8 * testelement.itemsize | |
except: | |
# We can't determine it from the array element's | |
# datatype, use a default of 8. | |
bitdepth = 8 | |
else: | |
# If we got here without exception, we now assume that | |
# the array is a numpy array. | |
if dtype.kind == 'b': | |
bitdepth = 1 | |
else: | |
bitdepth = 8 * dtype.itemsize | |
info['bitdepth'] = bitdepth | |
for thing in 'width height bitdepth greyscale alpha'.split(): | |
assert thing in info | |
return Image(a, info) | |
# So that refugee's from PIL feel more at home. Not documented. | |
fromarray = from_array | |
class Image: | |
"""A PNG image. | |
You can create an :class:`Image` object from an array of pixels by calling | |
:meth:`png.from_array`. It can be saved to disk with the | |
:meth:`save` method.""" | |
def __init__(self, rows, info): | |
""" | |
.. note :: | |
The constructor is not public. Please do not call it. | |
""" | |
self.rows = rows | |
self.info = info | |
def save(self, file): | |
"""Save the image to *file*. If *file* looks like an open file | |
descriptor then it is used, otherwise it is treated as a | |
filename and a fresh file is opened. | |
In general, you can only call this method once; after it has | |
been called the first time and the PNG image has been saved, the | |
source data will have been streamed, and cannot be streamed | |
again. | |
""" | |
w = Writer(**self.info) | |
try: | |
file.write | |
def close(): pass | |
except: | |
file = open(file, 'wb') | |
def close(): file.close() | |
try: | |
w.write(file, self.rows) | |
finally: | |
close() | |
class _readable: | |
""" | |
A simple file-like interface for strings and arrays. | |
""" | |
def __init__(self, buf): | |
self.buf = buf | |
self.offset = 0 | |
def read(self, n): | |
r = self.buf[self.offset:self.offset+n] | |
if isarray(r): | |
r = r.tostring() | |
self.offset += n | |
return r | |
class Reader: | |
""" | |
PNG decoder in pure Python. | |
""" | |
def __init__(self, _guess=None, **kw): | |
""" | |
Create a PNG decoder object. | |
The constructor expects exactly one keyword argument. If you | |
supply a positional argument instead, it will guess the input | |
type. You can choose among the following keyword arguments: | |
filename | |
Name of input file (a PNG file). | |
file | |
A file-like object (object with a read() method). | |
bytes | |
``array`` or ``string`` with PNG data. | |
""" | |
if ((_guess is not None and len(kw) != 0) or | |
(_guess is None and len(kw) != 1)): | |
raise TypeError("Reader() takes exactly 1 argument") | |
# Will be the first 8 bytes, later on. See validate_signature. | |
self.signature = None | |
self.transparent = None | |
# A pair of (len,type) if a chunk has been read but its data and | |
# checksum have not (in other words the file position is just | |
# past the 4 bytes that specify the chunk type). See preamble | |
# method for how this is used. | |
self.atchunk = None | |
if _guess is not None: | |
if isarray(_guess): | |
kw["bytes"] = _guess | |
elif isinstance(_guess, str): | |
kw["filename"] = _guess | |
elif isinstance(_guess, file): | |
kw["file"] = _guess | |
if "filename" in kw: | |
self.file = open(kw["filename"], "rb") | |
elif "file" in kw: | |
self.file = kw["file"] | |
elif "bytes" in kw: | |
self.file = _readable(kw["bytes"]) | |
else: | |
raise TypeError("expecting filename, file or bytes array") | |
def chunk(self, seek=None): | |
""" | |
Read the next PNG chunk from the input file; returns a | |
(*type*,*data*) tuple. *type* is the chunk's type as a string | |
(all PNG chunk types are 4 characters long). *data* is the | |
chunk's data content, as a string. | |
If the optional `seek` argument is | |
specified then it will keep reading chunks until it either runs | |
out of file or finds the type specified by the argument. Note | |
that in general the order of chunks in PNGs is unspecified, so | |
using `seek` can cause you to miss chunks. | |
""" | |
self.validate_signature() | |
while True: | |
# http://www.w3.org/TR/PNG/#5Chunk-layout | |
if not self.atchunk: | |
self.atchunk = self.chunklentype() | |
length,type = self.atchunk | |
self.atchunk = None | |
data = self.file.read(length) | |
if len(data) != length: | |
raise ChunkError('Chunk %s too short for required %i octets.' | |
% (type, length)) | |
checksum = self.file.read(4) | |
if len(checksum) != 4: | |
raise ValueError('Chunk %s too short for checksum.', tag) | |
if seek and type != seek: | |
continue | |
verify = zlib.crc32(strtobytes(type)) | |
verify = zlib.crc32(data, verify) | |
# Whether the output from zlib.crc32 is signed or not varies | |
# according to hideous implementation details, see | |
# http://bugs.python.org/issue1202 . | |
# We coerce it to be positive here (in a way which works on | |
# Python 2.3 and older). | |
verify &= 2**32 - 1 | |
verify = struct.pack('!I', verify) | |
if checksum != verify: | |
# print repr(checksum) | |
(a, ) = struct.unpack('!I', checksum) | |
(b, ) = struct.unpack('!I', verify) | |
raise ChunkError( | |
"Checksum error in %s chunk: 0x%08X != 0x%08X." % | |
(type, a, b)) | |
return type, data | |
def chunks(self): | |
"""Return an iterator that will yield each chunk as a | |
(*chunktype*, *content*) pair. | |
""" | |
while True: | |
t,v = self.chunk() | |
yield t,v | |
if t == 'IEND': | |
break | |
def undo_filter(self, filter_type, scanline, previous): | |
"""Undo the filter for a scanline. `scanline` is a sequence of | |
bytes that does not include the initial filter type byte. | |
`previous` is decoded previous scanline (for straightlaced | |
images this is the previous pixel row, but for interlaced | |
images, it is the previous scanline in the reduced image, which | |
in general is not the previous pixel row in the final image). | |
When there is no previous scanline (the first row of a | |
straightlaced image, or the first row in one of the passes in an | |
interlaced image), then this argument should be ``None``. | |
The scanline will have the effects of filtering removed, and the | |
result will be returned as a fresh sequence of bytes. | |
""" | |
# :todo: Would it be better to update scanline in place? | |
# Create the result byte array. It seems that the best way to | |
# create the array to be the right size is to copy from an | |
# existing sequence. *sigh* | |
# If we fill the result with scanline, then this allows a | |
# micro-optimisation in the "null" and "sub" cases. | |
result = array('B', scanline) | |
if filter_type == 0: | |
# And here, we _rely_ on filling the result with scanline, | |
# above. | |
return result | |
if filter_type not in (1,2,3,4): | |
raise FormatError('Invalid PNG Filter Type.' | |
' See http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters .') | |
# Filter unit. The stride from one pixel to the corresponding | |
# byte from the previous previous. Normally this is the pixel | |
# size in bytes, but when this is smaller than 1, the previous | |
# byte is used instead. | |
fu = max(1, self.psize) | |
# For the first line of a pass, synthesize a dummy previous | |
# line. An alternative approach would be to observe that on the | |
# first line 'up' is the same as 'null', 'paeth' is the same | |
# as 'sub', with only 'average' requiring any special case. | |
if not previous: | |
previous = array('B', [0]*len(scanline)) | |
def sub(): | |
"""Undo sub filter.""" | |
ai = 0 | |
# Loops starts at index fu. Observe that the initial part | |
# of the result is already filled in correctly with | |
# scanline. | |
for i in range(fu, len(result)): | |
x = scanline[i] | |
a = result[ai] | |
result[i] = (x + a) & 0xff | |
ai += 1 | |
def up(): | |
"""Undo up filter.""" | |
for i in range(len(result)): | |
x = scanline[i] | |
b = previous[i] | |
result[i] = (x + b) & 0xff | |
def average(): | |
"""Undo average filter.""" | |
ai = -fu | |
for i in range(len(result)): | |
x = scanline[i] | |
if ai < 0: | |
a = 0 | |
else: | |
a = result[ai] | |
b = previous[i] | |
result[i] = (x + ((a + b) >> 1)) & 0xff | |
ai += 1 | |
def paeth(): | |
"""Undo Paeth filter.""" | |
# Also used for ci. | |
ai = -fu | |
for i in range(len(result)): | |
x = scanline[i] | |
if ai < 0: | |
a = c = 0 | |
else: | |
a = result[ai] | |
c = previous[ai] | |
b = previous[i] | |
p = a + b - c | |
pa = abs(p - a) | |
pb = abs(p - b) | |
pc = abs(p - c) | |
if pa <= pb and pa <= pc: | |
pr = a | |
elif pb <= pc: | |
pr = b | |
else: | |
pr = c | |
result[i] = (x + pr) & 0xff | |
ai += 1 | |
# Call appropriate filter algorithm. Note that 0 has already | |
# been dealt with. | |
(None, sub, up, average, paeth)[filter_type]() | |
return result | |
def deinterlace(self, raw): | |
""" | |
Read raw pixel data, undo filters, deinterlace, and flatten. | |
Return in flat row flat pixel format. | |
""" | |
# print >> sys.stderr, ("Reading interlaced, w=%s, r=%s, planes=%s," + | |
# " bpp=%s") % (self.width, self.height, self.planes, self.bps) | |
# Values per row (of the target image) | |
vpr = self.width * self.planes | |
# Make a result array, and make it big enough. Interleaving | |
# writes to the output array randomly (well, not quite), so the | |
# entire output array must be in memory. | |
fmt = 'BH'[self.bitdepth > 8] | |
a = array(fmt, [0]*vpr*self.height) | |
source_offset = 0 | |
for xstart, ystart, xstep, ystep in _adam7: | |
# print >> sys.stderr, "Adam7: start=%s,%s step=%s,%s" % ( | |
# xstart, ystart, xstep, ystep) | |
if xstart >= self.width: | |
continue | |
# The previous (reconstructed) scanline. None at the | |
# beginning of a pass to indicate that there is no previous | |
# line. | |
recon = None | |
# Pixels per row (reduced pass image) | |
ppr = int(math.ceil((self.width-xstart)/float(xstep))) | |
# Row size in bytes for this pass. | |
row_size = int(math.ceil(self.psize * ppr)) | |
for y in range(ystart, self.height, ystep): | |
filter_type = raw[source_offset] | |
source_offset += 1 | |
scanline = raw[source_offset:source_offset+row_size] | |
source_offset += row_size | |
recon = self.undo_filter(filter_type, scanline, recon) | |
# Convert so that there is one element per pixel value | |
flat = self.serialtoflat(recon, ppr) | |
if xstep == 1: | |
assert xstart == 0 | |
offset = y * vpr | |
a[offset:offset+vpr] = flat | |
else: | |
offset = y * vpr + xstart * self.planes | |
end_offset = (y+1) * vpr | |
skip = self.planes * xstep | |
for i in range(self.planes): | |
a[offset+i:end_offset:skip] = \ | |
flat[i::self.planes] | |
return a | |
def iterboxed(self, rows): | |
"""Iterator that yields each scanline in boxed row flat pixel | |
format. `rows` should be an iterator that yields the bytes of | |
each row in turn. | |
""" | |
def asvalues(raw): | |
"""Convert a row of raw bytes into a flat row. Result may | |
or may not share with argument""" | |
if self.bitdepth == 8: | |
return raw | |
if self.bitdepth == 16: | |
raw = tostring(raw) | |
return array('H', struct.unpack('!%dH' % (len(raw)//2), raw)) | |
assert self.bitdepth < 8 | |
width = self.width | |
# Samples per byte | |
spb = 8//self.bitdepth | |
out = array('B') | |
mask = 2**self.bitdepth - 1 | |
shifts = list(map(self.bitdepth.__mul__, reversed(list(range(spb))))) | |
for o in raw: | |
out.extend([mask&(o>>i) for i in shifts]) | |
return out[:width] | |
return map(asvalues, rows) | |
def serialtoflat(self, bytes, width=None): | |
"""Convert serial format (byte stream) pixel data to flat row | |
flat pixel. | |
""" | |
if self.bitdepth == 8: | |
return bytes | |
if self.bitdepth == 16: | |
bytes = tostring(bytes) | |
return array('H', | |
struct.unpack('!%dH' % (len(bytes)//2), bytes)) | |
assert self.bitdepth < 8 | |
if width is None: | |
width = self.width | |
# Samples per byte | |
spb = 8//self.bitdepth | |
out = array('B') | |
mask = 2**self.bitdepth - 1 | |
shifts = list(map(self.bitdepth.__mul__, reversed(list(range(spb))))) | |
l = width | |
for o in bytes: | |
out.extend([(mask&(o>>s)) for s in shifts][:l]) | |
l -= spb | |
if l <= 0: | |
l = width | |
return out | |
def iterstraight(self, raw): | |
"""Iterator that undoes the effect of filtering, and yields each | |
row in serialised format (as a sequence of bytes). Assumes input | |
is straightlaced. `raw` should be an iterable that yields the | |
raw bytes in chunks of arbitrary size.""" | |
# length of row, in bytes | |
rb = self.row_bytes | |
a = array('B') | |
# The previous (reconstructed) scanline. None indicates first | |
# line of image. | |
recon = None | |
for some in raw: | |
a.extend(some) | |
while len(a) >= rb + 1: | |
filter_type = a[0] | |
scanline = a[1:rb+1] | |
del a[:rb+1] | |
recon = self.undo_filter(filter_type, scanline, recon) | |
yield recon | |
if len(a) != 0: | |
# :file:format We get here with a file format error: when the | |
# available bytes (after decompressing) do not pack into exact | |
# rows. | |
raise FormatError( | |
'Wrong size for decompressed IDAT chunk.') | |
assert len(a) == 0 | |
def validate_signature(self): | |
"""If signature (header) has not been read then read and | |
validate it; otherwise do nothing. | |
""" | |
if self.signature: | |
return | |
self.signature = self.file.read(8) | |
if self.signature != _signature: | |
raise FormatError("PNG file has invalid signature.") | |
def preamble(self): | |
""" | |
Extract the image metadata by reading the initial part of the PNG | |
file up to the start of the ``IDAT`` chunk. All the chunks that | |
precede the ``IDAT`` chunk are read and either processed for | |
metadata or discarded. | |
""" | |
self.validate_signature() | |
while True: | |
if not self.atchunk: | |
self.atchunk = self.chunklentype() | |
if self.atchunk is None: | |
raise FormatError( | |
'This PNG file has no IDAT chunks.') | |
if self.atchunk[1] == 'IDAT': | |
return | |
self.process_chunk() | |
def chunklentype(self): | |
"""Reads just enough of the input to determine the next | |
chunk's length and type, returned as a (*length*, *type*) pair | |
where *type* is a string. If there are no more chunks, ``None`` | |
is returned. | |
""" | |
x = self.file.read(8) | |
if not x: | |
return None | |
if len(x) != 8: | |
raise FormatError( | |
'End of file whilst reading chunk length and type.') | |
length,type = struct.unpack('!I4s', x) | |
type = bytestostr(type) | |
if length > 2**31-1: | |
raise FormatError('Chunk %s is too large: %d.' % (type,length)) | |
return length,type | |
def process_chunk(self): | |
"""Process the next chunk and its data. This only processes the | |
following chunk types, all others are ignored: ``IHDR``, | |
``PLTE``, ``bKGD``, ``tRNS``, ``gAMA``, ``sBIT``. | |
""" | |
type, data = self.chunk() | |
if type == 'IHDR': | |
# http://www.w3.org/TR/PNG/#11IHDR | |
if len(data) != 13: | |
raise FormatError('IHDR chunk has incorrect length.') | |
(self.width, self.height, self.bitdepth, self.color_type, | |
self.compression, self.filter, | |
self.interlace) = struct.unpack("!2I5B", data) | |
# Check that the header specifies only valid combinations. | |
if self.bitdepth not in (1,2,4,8,16): | |
raise Error("invalid bit depth %d" % self.bitdepth) | |
if self.color_type not in (0,2,3,4,6): | |
raise Error("invalid colour type %d" % self.color_type) | |
# Check indexed (palettized) images have 8 or fewer bits | |
# per pixel; check only indexed or greyscale images have | |
# fewer than 8 bits per pixel. | |
if ((self.color_type & 1 and self.bitdepth > 8) or | |
(self.bitdepth < 8 and self.color_type not in (0,3))): | |
raise FormatError("Illegal combination of bit depth (%d)" | |
" and colour type (%d)." | |
" See http://www.w3.org/TR/2003/REC-PNG-20031110/#table111 ." | |
% (self.bitdepth, self.color_type)) | |
if self.compression != 0: | |
raise Error("unknown compression method %d" % self.compression) | |
if self.filter != 0: | |
raise FormatError("Unknown filter method %d," | |
" see http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters ." | |
% self.filter) | |
if self.interlace not in (0,1): | |
raise FormatError("Unknown interlace method %d," | |
" see http://www.w3.org/TR/2003/REC-PNG-20031110/#8InterlaceMethods ." | |
% self.interlace) | |
# Derived values | |
# http://www.w3.org/TR/PNG/#6Colour-values | |
colormap = bool(self.color_type & 1) | |
greyscale = not (self.color_type & 2) | |
alpha = bool(self.color_type & 4) | |
color_planes = (3,1)[greyscale or colormap] | |
planes = color_planes + alpha | |
self.colormap = colormap | |
self.greyscale = greyscale | |
self.alpha = alpha | |
self.color_planes = color_planes | |
self.planes = planes | |
self.psize = float(self.bitdepth)/float(8) * planes | |
if int(self.psize) == self.psize: | |
self.psize = int(self.psize) | |
self.row_bytes = int(math.ceil(self.width * self.psize)) | |
# Stores PLTE chunk if present, and is used to check | |
# chunk ordering constraints. | |
self.plte = None | |
# Stores tRNS chunk if present, and is used to check chunk | |
# ordering constraints. | |
self.trns = None | |
# Stores sbit chunk if present. | |
self.sbit = None | |
elif type == 'PLTE': | |
# http://www.w3.org/TR/PNG/#11PLTE | |
if self.plte: | |
warnings.warn("Multiple PLTE chunks present.") | |
self.plte = data | |
if len(data) % 3 != 0: | |
raise FormatError( | |
"PLTE chunk's length should be a multiple of 3.") | |
if len(data) > (2**self.bitdepth)*3: | |
raise FormatError("PLTE chunk is too long.") | |
if len(data) == 0: | |
raise FormatError("Empty PLTE is not allowed.") | |
elif type == 'bKGD': | |
try: | |
if self.colormap: | |
if not self.plte: | |
warnings.warn( | |
"PLTE chunk is required before bKGD chunk.") | |
self.background = struct.unpack('B', data) | |
else: | |
self.background = struct.unpack("!%dH" % self.color_planes, | |
data) | |
except struct.error: | |
raise FormatError("bKGD chunk has incorrect length.") | |
elif type == 'tRNS': | |
# http://www.w3.org/TR/PNG/#11tRNS | |
self.trns = data | |
if self.colormap: | |
if not self.plte: | |
warnings.warn("PLTE chunk is required before tRNS chunk.") | |
else: | |
if len(data) > len(self.plte)/3: | |
# Was warning, but promoted to Error as it | |
# would otherwise cause pain later on. | |
raise FormatError("tRNS chunk is too long.") | |
else: | |
if self.alpha: | |
raise FormatError( | |
"tRNS chunk is not valid with colour type %d." % | |
self.color_type) | |
try: | |
self.transparent = \ | |
struct.unpack("!%dH" % self.color_planes, data) | |
except struct.error: | |
raise FormatError("tRNS chunk has incorrect length.") | |
elif type == 'gAMA': | |
try: | |
self.gamma = struct.unpack("!L", data)[0] / 100000.0 | |
except struct.error: | |
raise FormatError("gAMA chunk has incorrect length.") | |
elif type == 'sBIT': | |
self.sbit = data | |
if (self.colormap and len(data) != 3 or | |
not self.colormap and len(data) != self.planes): | |
raise FormatError("sBIT chunk has incorrect length.") | |
def read(self): | |
""" | |
Read the PNG file and decode it. Returns (`width`, `height`, | |
`pixels`, `metadata`). | |
May use excessive memory. | |
`pixels` are returned in boxed row flat pixel format. | |
""" | |
def iteridat(): | |
"""Iterator that yields all the ``IDAT`` chunks as strings.""" | |
while True: | |
try: | |
type, data = self.chunk() | |
except ValueError as e: | |
raise ChunkError(e.args[0]) | |
if type == 'IEND': | |
# http://www.w3.org/TR/PNG/#11IEND | |
break | |
if type != 'IDAT': | |
continue | |
# type == 'IDAT' | |
# http://www.w3.org/TR/PNG/#11IDAT | |
if self.colormap and not self.plte: | |
warnings.warn("PLTE chunk is required before IDAT chunk") | |
yield data | |
def iterdecomp(idat): | |
"""Iterator that yields decompressed strings. `idat` should | |
be an iterator that yields the ``IDAT`` chunk data. | |
""" | |
# Currently, with no max_length paramter to decompress, this | |
# routine will do one yield per IDAT chunk. So not very | |
# incremental. | |
d = zlib.decompressobj() | |
# Each IDAT chunk is passed to the decompressor, then any | |
# remaining state is decompressed out. | |
for data in idat: | |
# :todo: add a max_length argument here to limit output | |
# size. | |
yield array('B', d.decompress(data)) | |
yield array('B', d.flush()) | |
self.preamble() | |
raw = iterdecomp(iteridat()) | |
if self.interlace: | |
raw = array('B', itertools.chain(*raw)) | |
arraycode = 'BH'[self.bitdepth>8] | |
# Like :meth:`group` but producing an array.array object for | |
# each row. | |
pixels = map(lambda *row: array(arraycode, row), | |
*[iter(self.deinterlace(raw))]*self.width*self.planes) | |
else: | |
pixels = self.iterboxed(self.iterstraight(raw)) | |
meta = dict() | |
for attr in 'greyscale alpha planes bitdepth interlace'.split(): | |
meta[attr] = getattr(self, attr) | |
meta['size'] = (self.width, self.height) | |
for attr in 'gamma transparent background'.split(): | |
a = getattr(self, attr, None) | |
if a is not None: | |
meta[attr] = a | |
return self.width, self.height, pixels, meta | |
def read_flat(self): | |
""" | |
Read a PNG file and decode it into flat row flat pixel format. | |
Returns (*width*, *height*, *pixels*, *metadata*). | |
May use excessive memory. | |
`pixels` are returned in flat row flat pixel format. | |
See also the :meth:`read` method which returns pixels in the | |
more stream-friendly boxed row flat pixel format. | |
""" | |
x, y, pixel, meta = self.read() | |
arraycode = 'BH'[meta['bitdepth']>8] | |
pixel = array(arraycode, itertools.chain(*pixel)) | |
return x, y, pixel, meta | |
def palette(self, alpha='natural'): | |
"""Returns a palette that is a sequence of 3-tuples or 4-tuples, | |
synthesizing it from the ``PLTE`` and ``tRNS`` chunks. These | |
chunks should have already been processed (for example, by | |
calling the :meth:`preamble` method). All the tuples are the | |
same size: 3-tuples if there is no ``tRNS`` chunk, 4-tuples when | |
there is a ``tRNS`` chunk. Assumes that the image is colour type | |
3 and therefore a ``PLTE`` chunk is required. | |
If the `alpha` argument is ``'force'`` then an alpha channel is | |
always added, forcing the result to be a sequence of 4-tuples. | |
""" | |
if not self.plte: | |
raise FormatError( | |
"Required PLTE chunk is missing in colour type 3 image.") | |
plte = group(array('B', self.plte), 3) | |
if self.trns or alpha == 'force': | |
trns = array('B', self.trns or '') | |
trns.extend([255]*(len(plte)-len(trns))) | |
plte = list(map(operator.add, plte, group(trns, 1))) | |
return plte | |
def asDirect(self): | |
"""Returns the image data as a direct representation of an | |
``x * y * planes`` array. This method is intended to remove the | |
need for callers to deal with palettes and transparency | |
themselves. Images with a palette (colour type 3) | |
are converted to RGB or RGBA; images with transparency (a | |
``tRNS`` chunk) are converted to LA or RGBA as appropriate. | |
When returned in this format the pixel values represent the | |
colour value directly without needing to refer to palettes or | |
transparency information. | |
Like the :meth:`read` method this method returns a 4-tuple: | |
(*width*, *height*, *pixels*, *meta*) | |
This method normally returns pixel values with the bit depth | |
they have in the source image, but when the source PNG has an | |
``sBIT`` chunk it is inspected and can reduce the bit depth of | |
the result pixels; pixel values will be reduced according to | |
the bit depth specified in the ``sBIT`` chunk (PNG nerds should | |
note a single result bit depth is used for all channels; the | |
maximum of the ones specified in the ``sBIT`` chunk. An RGB565 | |
image will be rescaled to 6-bit RGB666). | |
The *meta* dictionary that is returned reflects the `direct` | |
format and not the original source image. For example, an RGB | |
source image with a ``tRNS`` chunk to represent a transparent | |
colour, will have ``planes=3`` and ``alpha=False`` for the | |
source image, but the *meta* dictionary returned by this method | |
will have ``planes=4`` and ``alpha=True`` because an alpha | |
channel is synthesized and added. | |
*pixels* is the pixel data in boxed row flat pixel format (just | |
like the :meth:`read` method). | |
All the other aspects of the image data are not changed. | |
""" | |
self.preamble() | |
# Simple case, no conversion necessary. | |
if not self.colormap and not self.trns and not self.sbit: | |
return self.read() | |
x,y,pixels,meta = self.read() | |
if self.colormap: | |
meta['colormap'] = False | |
meta['alpha'] = bool(self.trns) | |
meta['bitdepth'] = 8 | |
meta['planes'] = 3 + bool(self.trns) | |
plte = self.palette() | |
def iterpal(pixels): | |
for row in pixels: | |
row = list(map(plte.__getitem__, row)) | |
yield array('B', itertools.chain(*row)) | |
pixels = iterpal(pixels) | |
elif self.trns: | |
# It would be nice if there was some reasonable way of doing | |
# this without generating a whole load of intermediate tuples. | |
# But tuples does seem like the easiest way, with no other way | |
# clearly much simpler or much faster. (Actually, the L to LA | |
# conversion could perhaps go faster (all those 1-tuples!), but | |
# I still wonder whether the code proliferation is worth it) | |
it = self.transparent | |
maxval = 2**meta['bitdepth']-1 | |
planes = meta['planes'] | |
meta['alpha'] = True | |
meta['planes'] += 1 | |
typecode = 'BH'[meta['bitdepth']>8] | |
def itertrns(pixels): | |
for row in pixels: | |
# For each row we group it into pixels, then form a | |
# characterisation vector that says whether each pixel | |
# is opaque or not. Then we convert True/False to | |
# 0/maxval (by multiplication), and add it as the extra | |
# channel. | |
row = group(row, planes) | |
opa = list(map(it.__ne__, row)) | |
opa = list(map(maxval.__mul__, opa)) | |
opa = list(zip(opa)) # convert to 1-tuples | |
yield array(typecode, | |
itertools.chain(*list(map(operator.add, row, opa)))) | |
pixels = itertrns(pixels) | |
targetbitdepth = None | |
if self.sbit: | |
sbit = struct.unpack('%dB' % len(self.sbit), self.sbit) | |
targetbitdepth = max(sbit) | |
if targetbitdepth > meta['bitdepth']: | |
raise Error('sBIT chunk %r exceeds bitdepth %d' % | |
(sbit,self.bitdepth)) | |
if min(sbit) <= 0: | |
raise Error('sBIT chunk %r has a 0-entry' % sbit) | |
if targetbitdepth == meta['bitdepth']: | |
targetbitdepth = None | |
if targetbitdepth: | |
shift = meta['bitdepth'] - targetbitdepth | |
meta['bitdepth'] = targetbitdepth | |
def itershift(pixels): | |
for row in pixels: | |
yield list(map(shift.__rrshift__, row)) | |
pixels = itershift(pixels) | |
return x,y,pixels,meta | |
def asFloat(self, maxval=1.0): | |
"""Return image pixels as per :meth:`asDirect` method, but scale | |
all pixel values to be floating point values between 0.0 and | |
*maxval*. | |
""" | |
x,y,pixels,info = self.asDirect() | |
sourcemaxval = 2**info['bitdepth']-1 | |
del info['bitdepth'] | |
info['maxval'] = float(maxval) | |
factor = float(maxval)/float(sourcemaxval) | |
def iterfloat(): | |
for row in pixels: | |
yield list(map(factor.__mul__, row)) | |
return x,y,iterfloat(),info | |
def _as_rescale(self, get, targetbitdepth): | |
"""Helper used by :meth:`asRGB8` and :meth:`asRGBA8`.""" | |
width,height,pixels,meta = get() | |
maxval = 2**meta['bitdepth'] - 1 | |
targetmaxval = 2**targetbitdepth - 1 | |
factor = float(targetmaxval) / float(maxval) | |
meta['bitdepth'] = targetbitdepth | |
def iterscale(): | |
for row in pixels: | |
yield [int(round(x*factor)) for x in row] | |
return width, height, iterscale(), meta | |
def asRGB8(self): | |
"""Return the image data as an RGB pixels with 8-bits per | |
sample. This is like the :meth:`asRGB` method except that | |
this method additionally rescales the values so that they | |
are all between 0 and 255 (8-bit). In the case where the | |
source image has a bit depth < 8 the transformation preserves | |
all the information; where the source image has bit depth | |
> 8, then rescaling to 8-bit values loses precision. No | |
dithering is performed. Like :meth:`asRGB`, an alpha channel | |
in the source image will raise an exception. | |
This function returns a 4-tuple: | |
(*width*, *height*, *pixels*, *metadata*). | |
*width*, *height*, *metadata* are as per the :meth:`read` method. | |
*pixels* is the pixel data in boxed row flat pixel format. | |
""" | |
return self._as_rescale(self.asRGB, 8) | |
def asRGBA8(self): | |
"""Return the image data as RGBA pixels with 8-bits per | |
sample. This method is similar to :meth:`asRGB8` and | |
:meth:`asRGBA`: The result pixels have an alpha channel, *and* | |
values are rescaled to the range 0 to 255. The alpha channel is | |
synthesized if necessary (with a small speed penalty). | |
""" | |
return self._as_rescale(self.asRGBA, 8) | |
def asRGB(self): | |
"""Return image as RGB pixels. RGB colour images are passed | |
through unchanged; greyscales are expanded into RGB | |
triplets (there is a small speed overhead for doing this). | |
An alpha channel in the source image will raise an | |
exception. | |
The return values are as for the :meth:`read` method | |
except that the *metadata* reflect the returned pixels, not the | |
source image. In particular, for this method | |
``metadata['greyscale']`` will be ``False``. | |
""" | |
width,height,pixels,meta = self.asDirect() | |
if meta['alpha']: | |
raise Error("will not convert image with alpha channel to RGB") | |
if not meta['greyscale']: | |
return width,height,pixels,meta | |
meta['greyscale'] = False | |
typecode = 'BH'[meta['bitdepth'] > 8] | |
def iterrgb(): | |
for row in pixels: | |
a = array(typecode, [0]) * 3 * width | |
for i in range(3): | |
a[i::3] = row | |
yield a | |
return width,height,iterrgb(),meta | |
def asRGBA(self): | |
"""Return image as RGBA pixels. Greyscales are expanded into | |
RGB triplets; an alpha channel is synthesized if necessary. | |
The return values are as for the :meth:`read` method | |
except that the *metadata* reflect the returned pixels, not the | |
source image. In particular, for this method | |
``metadata['greyscale']`` will be ``False``, and | |
``metadata['alpha']`` will be ``True``. | |
""" | |
width,height,pixels,meta = self.asDirect() | |
if meta['alpha'] and not meta['greyscale']: | |
return width,height,pixels,meta | |
typecode = 'BH'[meta['bitdepth'] > 8] | |
maxval = 2**meta['bitdepth'] - 1 | |
def newarray(): | |
return array(typecode, [0]) * 4 * width | |
if meta['alpha'] and meta['greyscale']: | |
# LA to RGBA | |
def convert(): | |
for row in pixels: | |
# Create a fresh target row, then copy L channel | |
# into first three target channels, and A channel | |
# into fourth channel. | |
a = newarray() | |
for i in range(3): | |
a[i::4] = row[0::2] | |
a[3::4] = row[1::2] | |
yield a | |
elif meta['greyscale']: | |
# L to RGBA | |
def convert(): | |
for row in pixels: | |
a = newarray() | |
for i in range(3): | |
a[i::4] = row | |
a[3::4] = array(typecode, [maxval]) * width | |
yield a | |
else: | |
assert not meta['alpha'] and not meta['greyscale'] | |
# RGB to RGBA | |
def convert(): | |
for row in pixels: | |
a = newarray() | |
for i in range(3): | |
a[i::4] = row[i::3] | |
a[3::4] = array(typecode, [maxval]) * width | |
yield a | |
meta['alpha'] = True | |
meta['greyscale'] = False | |
return width,height,convert(),meta | |
# === Legacy Version Support === | |
# :pyver:old: PyPNG works on Python versions 2.3 and 2.2, but not | |
# without some awkward problems. Really PyPNG works on Python 2.4 (and | |
# above); it works on Pythons 2.3 and 2.2 by virtue of fixing up | |
# problems here. It's a bit ugly (which is why it's hidden down here). | |
# | |
# Generally the strategy is one of pretending that we're running on | |
# Python 2.4 (or above), and patching up the library support on earlier | |
# versions so that it looks enough like Python 2.4. When it comes to | |
# Python 2.2 there is one thing we cannot patch: extended slices | |
# http://www.python.org/doc/2.3/whatsnew/section-slices.html. | |
# Instead we simply declare that features that are implemented using | |
# extended slices will not work on Python 2.2. | |
# | |
# In order to work on Python 2.3 we fix up a recurring annoyance involving | |
# the array type. In Python 2.3 an array cannot be initialised with an | |
# array, and it cannot be extended with a list (or other sequence). | |
# Both of those are repeated issues in the code. Whilst I would not | |
# normally tolerate this sort of behaviour, here we "shim" a replacement | |
# for array into place (and hope no-ones notices). You never read this. | |
# | |
# In an amusing case of warty hacks on top of warty hacks... the array | |
# shimming we try and do only works on Python 2.3 and above (you can't | |
# subclass array.array in Python 2.2). So to get it working on Python | |
# 2.2 we go for something much simpler and (probably) way slower. | |
try: | |
array('B').extend([]) | |
array('B', array('B')) | |
except: | |
# Expect to get here on Python 2.3 | |
try: | |
class _array_shim(array): | |
true_array = array | |
def __new__(cls, typecode, init=None): | |
super_new = super(_array_shim, cls).__new__ | |
it = super_new(cls, typecode) | |
if init is None: | |
return it | |
it.extend(init) | |
return it | |
def extend(self, extension): | |
super_extend = super(_array_shim, self).extend | |
if isinstance(extension, self.true_array): | |
return super_extend(extension) | |
if not isinstance(extension, (list, str)): | |
# Convert to list. Allows iterators to work. | |
extension = list(extension) | |
return super_extend(self.true_array(self.typecode, extension)) | |
array = _array_shim | |
except: | |
# Expect to get here on Python 2.2 | |
def array(typecode, init=()): | |
if type(init) == str: | |
return list(map(ord, init)) | |
return list(init) | |
# Further hacks to get it limping along on Python 2.2 | |
try: | |
enumerate | |
except: | |
def enumerate(seq): | |
i=0 | |
for x in seq: | |
yield i,x | |
i += 1 | |
try: | |
reversed | |
except: | |
def reversed(l): | |
l = list(l) | |
l.reverse() | |
for x in l: | |
yield x | |
try: | |
itertools | |
except: | |
class _dummy_itertools: | |
pass | |
itertools = _dummy_itertools() | |
def _itertools_imap(f, seq): | |
for x in seq: | |
yield f(x) | |
itertools.imap = _itertools_imap | |
def _itertools_chain(*iterables): | |
for it in iterables: | |
for element in it: | |
yield element | |
itertools.chain = _itertools_chain | |
# === Internal Test Support === | |
# This section comprises the tests that are internally validated (as | |
# opposed to tests which produce output files that are externally | |
# validated). Primarily they are unittests. | |
# Note that it is difficult to internally validate the results of | |
# writing a PNG file. The only thing we can do is read it back in | |
# again, which merely checks consistency, not that the PNG file we | |
# produce is valid. | |
# Run the tests from the command line: | |
# python -c 'import png;png.test()' | |
# (For an in-memory binary file IO object) We use BytesIO where | |
# available, otherwise we use StringIO, but name it BytesIO. | |
try: | |
from io import BytesIO | |
except: | |
from io import StringIO as BytesIO | |
import tempfile | |
# http://www.python.org/doc/2.4.4/lib/module-unittest.html | |
import unittest | |
def test(): | |
unittest.main(__name__) | |
def topngbytes(name, rows, x, y, **k): | |
"""Convenience function for creating a PNG file "in memory" as a | |
string. Creates a :class:`Writer` instance using the keyword arguments, | |
then passes `rows` to its :meth:`Writer.write` method. The resulting | |
PNG file is returned as a string. `name` is used to identify the file for | |
debugging. | |
""" | |
import os | |
print(name) | |
f = BytesIO() | |
w = Writer(x, y, **k) | |
w.write(f, rows) | |
if os.environ.get('PYPNG_TEST_TMP'): | |
w = open(name, 'wb') | |
w.write(f.getvalue()) | |
w.close() | |
return f.getvalue() | |
def testWithIO(inp, out, f): | |
"""Calls the function `f` with ``sys.stdin`` changed to `inp` | |
and ``sys.stdout`` changed to `out`. They are restored when `f` | |
returns. This function returns whatever `f` returns. | |
""" | |
import os | |
try: | |
oldin,sys.stdin = sys.stdin,inp | |
oldout,sys.stdout = sys.stdout,out | |
x = f() | |
finally: | |
sys.stdin = oldin | |
sys.stdout = oldout | |
if os.environ.get('PYPNG_TEST_TMP') and hasattr(out,'getvalue'): | |
name = mycallersname() | |
if name: | |
w = open(name+'.png', 'wb') | |
w.write(out.getvalue()) | |
w.close() | |
return x | |
def mycallersname(): | |
"""Returns the name of the caller of the caller of this function | |
(hence the name of the caller of the function in which | |
"mycallersname()" textually appears). Returns None if this cannot | |
be determined.""" | |
# http://docs.python.org/library/inspect.html#the-interpreter-stack | |
import inspect | |
frame = inspect.currentframe() | |
if not frame: | |
return None | |
frame_,filename_,lineno_,funname,linelist_,listi_ = ( | |
inspect.getouterframes(frame)[2]) | |
return funname | |
def seqtobytes(s): | |
"""Convert a sequence of integers to a *bytes* instance. Good for | |
plastering over Python 2 / Python 3 cracks. | |
""" | |
return strtobytes(''.join(chr(x) for x in s)) | |
class Test(unittest.TestCase): | |
# This member is used by the superclass. If we don't define a new | |
# class here then when we use self.assertRaises() and the PyPNG code | |
# raises an assertion then we get no proper traceback. I can't work | |
# out why, but defining a new class here means we get a proper | |
# traceback. | |
class failureException(Exception): | |
pass | |
def helperLN(self, n): | |
mask = (1 << n) - 1 | |
# Use small chunk_limit so that multiple chunk writing is | |
# tested. Making it a test for Issue 20. | |
w = Writer(15, 17, greyscale=True, bitdepth=n, chunk_limit=99) | |
f = BytesIO() | |
w.write_array(f, array('B', list(map(mask.__and__, list(range(1, 256)))))) | |
r = Reader(bytes=f.getvalue()) | |
x,y,pixels,meta = r.read() | |
self.assertEqual(x, 15) | |
self.assertEqual(y, 17) | |
self.assertEqual(list(itertools.chain(*pixels)), | |
list(map(mask.__and__, list(range(1,256))))) | |
def testL8(self): | |
return self.helperLN(8) | |
def testL4(self): | |
return self.helperLN(4) | |
def testL2(self): | |
"Also tests asRGB8." | |
w = Writer(1, 4, greyscale=True, bitdepth=2) | |
f = BytesIO() | |
w.write_array(f, array('B', list(range(4)))) | |
r = Reader(bytes=f.getvalue()) | |
x,y,pixels,meta = r.asRGB8() | |
self.assertEqual(x, 1) | |
self.assertEqual(y, 4) | |
for i,row in enumerate(pixels): | |
self.assertEqual(len(row), 3) | |
self.assertEqual(list(row), [0x55*i]*3) | |
def testP2(self): | |
"2-bit palette." | |
a = (255,255,255) | |
b = (200,120,120) | |
c = (50,99,50) | |
w = Writer(1, 4, bitdepth=2, palette=[a,b,c]) | |
f = BytesIO() | |
w.write_array(f, array('B', (0,1,1,2))) | |
r = Reader(bytes=f.getvalue()) | |
x,y,pixels,meta = r.asRGB8() | |
self.assertEqual(x, 1) | |
self.assertEqual(y, 4) | |
self.assertEqual(list(pixels), list(map(list, [a, b, b, c]))) | |
def testPtrns(self): | |
"Test colour type 3 and tRNS chunk (and 4-bit palette)." | |
a = (50,99,50,50) | |
b = (200,120,120,80) | |
c = (255,255,255) | |
d = (200,120,120) | |
e = (50,99,50) | |
w = Writer(3, 3, bitdepth=4, palette=[a,b,c,d,e]) | |
f = BytesIO() | |
w.write_array(f, array('B', (4, 3, 2, 3, 2, 0, 2, 0, 1))) | |
r = Reader(bytes=f.getvalue()) | |
x,y,pixels,meta = r.asRGBA8() | |
self.assertEqual(x, 3) | |
self.assertEqual(y, 3) | |
c = c+(255,) | |
d = d+(255,) | |
e = e+(255,) | |
boxed = [(e,d,c),(d,c,a),(c,a,b)] | |
flat = [itertools.chain(*row) for row in boxed] | |
self.assertEqual(list(map(list, pixels)), list(map(list, flat))) | |
def testRGBtoRGBA(self): | |
"asRGBA8() on colour type 2 source.""" | |
# Test for Issue 26 | |
r = Reader(bytes=_pngsuite['basn2c08']) | |
x,y,pixels,meta = r.asRGBA8() | |
# Test the pixels at row 9 columns 0 and 1. | |
row9 = list(pixels)[9] | |
self.assertEqual(row9[0:8], | |
[0xff, 0xdf, 0xff, 0xff, 0xff, 0xde, 0xff, 0xff]) | |
def testLtoRGBA(self): | |
"asRGBA() on grey source.""" | |
# Test for Issue 60 | |
r = Reader(bytes=_pngsuite['basi0g08']) | |
x,y,pixels,meta = r.asRGBA() | |
row9 = list(list(pixels)[9]) | |
self.assertEqual(row9[0:8], | |
[222, 222, 222, 255, 221, 221, 221, 255]) | |
def testCtrns(self): | |
"Test colour type 2 and tRNS chunk." | |
# Test for Issue 25 | |
r = Reader(bytes=_pngsuite['tbrn2c08']) | |
x,y,pixels,meta = r.asRGBA8() | |
# I just happen to know that the first pixel is transparent. | |
# In particular it should be #7f7f7f00 | |
row0 = list(pixels)[0] | |
self.assertEqual(tuple(row0[0:4]), (0x7f, 0x7f, 0x7f, 0x00)) | |
def testAdam7read(self): | |
"""Adam7 interlace reading. | |
Specifically, test that for images in the PngSuite that | |
have both an interlaced and straightlaced pair that both | |
images from the pair produce the same array of pixels.""" | |
for candidate in _pngsuite: | |
if not candidate.startswith('basn'): | |
continue | |
candi = candidate.replace('n', 'i') | |
if candi not in _pngsuite: | |
continue | |
print('adam7 read', candidate) | |
straight = Reader(bytes=_pngsuite[candidate]) | |
adam7 = Reader(bytes=_pngsuite[candi]) | |
# Just compare the pixels. Ignore x,y (because they're | |
# likely to be correct?); metadata is ignored because the | |
# "interlace" member differs. Lame. | |
straight = straight.read()[2] | |
adam7 = adam7.read()[2] | |
self.assertEqual(list(map(list, straight)), list(map(list, adam7))) | |
def testAdam7write(self): | |
"""Adam7 interlace writing. | |
For each test image in the PngSuite, write an interlaced | |
and a straightlaced version. Decode both, and compare results. | |
""" | |
# Not such a great test, because the only way we can check what | |
# we have written is to read it back again. | |
for name,bytes in list(_pngsuite.items()): | |
# Only certain colour types supported for this test. | |
if name[3:5] not in ['n0', 'n2', 'n4', 'n6']: | |
continue | |
it = Reader(bytes=bytes) | |
x,y,pixels,meta = it.read() | |
pngi = topngbytes('adam7wn'+name+'.png', pixels, | |
x=x, y=y, bitdepth=it.bitdepth, | |
greyscale=it.greyscale, alpha=it.alpha, | |
transparent=it.transparent, | |
interlace=False) | |
x,y,ps,meta = Reader(bytes=pngi).read() | |
it = Reader(bytes=bytes) | |
x,y,pixels,meta = it.read() | |
pngs = topngbytes('adam7wi'+name+'.png', pixels, | |
x=x, y=y, bitdepth=it.bitdepth, | |
greyscale=it.greyscale, alpha=it.alpha, | |
transparent=it.transparent, | |
interlace=True) | |
x,y,pi,meta = Reader(bytes=pngs).read() | |
self.assertEqual(list(map(list, ps)), list(map(list, pi))) | |
def testPGMin(self): | |
"""Test that the command line tool can read PGM files.""" | |
def do(): | |
return _main(['testPGMin']) | |
s = BytesIO() | |
s.write(strtobytes('P5 2 2 3\n')) | |
s.write(strtobytes('\x00\x01\x02\x03')) | |
s.flush() | |
s.seek(0) | |
o = BytesIO() | |
testWithIO(s, o, do) | |
r = Reader(bytes=o.getvalue()) | |
x,y,pixels,meta = r.read() | |
self.assertTrue(r.greyscale) | |
self.assertEqual(r.bitdepth, 2) | |
def testPAMin(self): | |
"""Test that the command line tool can read PAM file.""" | |
def do(): | |
return _main(['testPAMin']) | |
s = BytesIO() | |
s.write(strtobytes('P7\nWIDTH 3\nHEIGHT 1\nDEPTH 4\nMAXVAL 255\n' | |
'TUPLTYPE RGB_ALPHA\nENDHDR\n')) | |
# The pixels in flat row flat pixel format | |
flat = [255,0,0,255, 0,255,0,120, 0,0,255,30] | |
asbytes = seqtobytes(flat) | |
s.write(asbytes) | |
s.flush() | |
s.seek(0) | |
o = BytesIO() | |
testWithIO(s, o, do) | |
r = Reader(bytes=o.getvalue()) | |
x,y,pixels,meta = r.read() | |
self.assertTrue(r.alpha) | |
self.assertTrue(not r.greyscale) | |
self.assertEqual(list(itertools.chain(*pixels)), flat) | |
def testLA4(self): | |
"""Create an LA image with bitdepth 4.""" | |
bytes = topngbytes('la4.png', [[5, 12]], 1, 1, | |
greyscale=True, alpha=True, bitdepth=4) | |
sbit = Reader(bytes=bytes).chunk('sBIT')[1] | |
self.assertEqual(sbit, strtobytes('\x04\x04')) | |
def testPNMsbit(self): | |
"""Test that PNM files can generates sBIT chunk.""" | |
def do(): | |
return _main(['testPNMsbit']) | |
s = BytesIO() | |
s.write(strtobytes('P6 8 1 1\n')) | |
for pixel in range(8): | |
s.write(struct.pack('<I', (0x4081*pixel)&0x10101)[:3]) | |
s.flush() | |
s.seek(0) | |
o = BytesIO() | |
testWithIO(s, o, do) | |
r = Reader(bytes=o.getvalue()) | |
sbit = r.chunk('sBIT')[1] | |
self.assertEqual(sbit, strtobytes('\x01\x01\x01')) | |
def testLtrns0(self): | |
"""Create greyscale image with tRNS chunk.""" | |
return self.helperLtrns(0) | |
def testLtrns1(self): | |
"""Using 1-tuple for transparent arg.""" | |
return self.helperLtrns((0,)) | |
def helperLtrns(self, transparent): | |
"""Helper used by :meth:`testLtrns*`.""" | |
pixels = list(zip([0x00, 0x38, 0x4c, 0x54, 0x5c, 0x40, 0x38, 0x00])) | |
o = BytesIO() | |
w = Writer(8, 8, greyscale=True, bitdepth=1, transparent=transparent) | |
w.write_packed(o, pixels) | |
r = Reader(bytes=o.getvalue()) | |
x,y,pixels,meta = r.asDirect() | |
self.assertTrue(meta['alpha']) | |
self.assertTrue(meta['greyscale']) | |
self.assertEqual(meta['bitdepth'], 1) | |
def testWinfo(self): | |
"""Test the dictionary returned by a `read` method can be used | |
as args for :meth:`Writer`. | |
""" | |
r = Reader(bytes=_pngsuite['basn2c16']) | |
info = r.read()[3] | |
w = Writer(**info) | |
def testPackedIter(self): | |
"""Test iterator for row when using write_packed. | |
Indicative for Issue 47. | |
""" | |
w = Writer(16, 2, greyscale=True, alpha=False, bitdepth=1) | |
o = BytesIO() | |
w.write_packed(o, [itertools.chain([0x0a], [0xaa]), | |
itertools.chain([0x0f], [0xff])]) | |
r = Reader(bytes=o.getvalue()) | |
x,y,pixels,info = r.asDirect() | |
pixels = list(pixels) | |
self.assertEqual(len(pixels), 2) | |
self.assertEqual(len(pixels[0]), 16) | |
def testInterlacedArray(self): | |
"""Test that reading an interlaced PNG yields each row as an | |
array.""" | |
r = Reader(bytes=_pngsuite['basi0g08']) | |
list(r.read()[2])[0].tostring | |
def testTrnsArray(self): | |
"""Test that reading a type 2 PNG with tRNS chunk yields each | |
row as an array (using asDirect).""" | |
r = Reader(bytes=_pngsuite['tbrn2c08']) | |
list(r.asDirect()[2])[0].tostring | |
# Invalid file format tests. These construct various badly | |
# formatted PNG files, then feed them into a Reader. When | |
# everything is working properly, we should get FormatError | |
# exceptions raised. | |
def testEmpty(self): | |
"""Test empty file.""" | |
r = Reader(bytes='') | |
self.assertRaises(FormatError, r.asDirect) | |
def testSigOnly(self): | |
"""Test file containing just signature bytes.""" | |
r = Reader(bytes=_signature) | |
self.assertRaises(FormatError, r.asDirect) | |
def testExtraPixels(self): | |
"""Test file that contains too many pixels.""" | |
def eachchunk(chunk): | |
if chunk[0] != 'IDAT': | |
return chunk | |
data = zlib.decompress(chunk[1]) | |
data += strtobytes('\x00garbage') | |
data = zlib.compress(data) | |
chunk = (chunk[0], data) | |
return chunk | |
self.assertRaises(FormatError, self.helperFormat, eachchunk) | |
def testNotEnoughPixels(self): | |
def eachchunk(chunk): | |
if chunk[0] != 'IDAT': | |
return chunk | |
# Remove last byte. | |
data = zlib.decompress(chunk[1]) | |
data = data[:-1] | |
data = zlib.compress(data) | |
return (chunk[0], data) | |
self.assertRaises(FormatError, self.helperFormat, eachchunk) | |
def helperFormat(self, f): | |
r = Reader(bytes=_pngsuite['basn0g01']) | |
o = BytesIO() | |
def newchunks(): | |
for chunk in r.chunks(): | |
yield f(chunk) | |
write_chunks(o, newchunks()) | |
r = Reader(bytes=o.getvalue()) | |
return list(r.asDirect()[2]) | |
def testBadFilter(self): | |
def eachchunk(chunk): | |
if chunk[0] != 'IDAT': | |
return chunk | |
data = zlib.decompress(chunk[1]) | |
# Corrupt the first filter byte | |
data = strtobytes('\x99') + data[1:] | |
data = zlib.compress(data) | |
return (chunk[0], data) | |
self.assertRaises(FormatError, self.helperFormat, eachchunk) | |
def testFlat(self): | |
"""Test read_flat.""" | |
import hashlib | |
r = Reader(bytes=_pngsuite['basn0g02']) | |
x,y,pixel,meta = r.read_flat() | |
d = hashlib.md5(seqtobytes(pixel)).digest() | |
self.assertEqual(_enhex(d), '255cd971ab8cd9e7275ff906e5041aa0') | |
def testfromarray(self): | |
img = from_array([[0, 0x33, 0x66], [0xff, 0xcc, 0x99]], 'L') | |
img.save('testfromarray.png') | |
def testfromarrayL16(self): | |
img = from_array(group(list(range(2**16)), 256), 'L;16') | |
img.save('testL16.png') | |
def testfromarrayRGB(self): | |
img = from_array([[0,0,0, 0,0,1, 0,1,0, 0,1,1], | |
[1,0,0, 1,0,1, 1,1,0, 1,1,1]], 'RGB;1') | |
o = BytesIO() | |
img.save(o) | |
def testfromarrayIter(self): | |
import itertools | |
i = itertools.islice(itertools.count(10), 20) | |
i = map(lambda x: [x, x, x], i) | |
img = from_array(i, 'RGB;5', dict(height=20)) | |
f = open('testiter.png', 'wb') | |
img.save(f) | |
f.close() | |
# numpy dependent tests. These are skipped (with a message to | |
# sys.stderr) if numpy cannot be imported. | |
def testNumpyuint16(self): | |
"""numpy uint16.""" | |
try: | |
import numpy | |
except ImportError: | |
print("skipping numpy test", file=sys.stderr) | |
return | |
rows = [list(map(numpy.uint16, list(range(0,0x10000,0x5555))))] | |
b = topngbytes('numpyuint16.png', rows, 4, 1, | |
greyscale=True, alpha=False, bitdepth=16) | |
def testNumpyuint8(self): | |
"""numpy uint8.""" | |
try: | |
import numpy | |
except ImportError: | |
print("skipping numpy test", file=sys.stderr) | |
return | |
rows = [list(map(numpy.uint8, list(range(0,0x100,0x55))))] | |
b = topngbytes('numpyuint8.png', rows, 4, 1, | |
greyscale=True, alpha=False, bitdepth=8) | |
def testNumpybool(self): | |
"""numpy bool.""" | |
try: | |
import numpy | |
except ImportError: | |
print("skipping numpy test", file=sys.stderr) | |
return | |
rows = [list(map(numpy.bool, [0,1]))] | |
b = topngbytes('numpybool.png', rows, 2, 1, | |
greyscale=True, alpha=False, bitdepth=1) | |
def testNumpyarray(self): | |
"""numpy array.""" | |
try: | |
import numpy | |
except ImportError: | |
print("skipping numpy test", file=sys.stderr) | |
return | |
pixels = numpy.array([[0,0x5555],[0x5555,0xaaaa]], numpy.uint16) | |
img = from_array(pixels, 'L') | |
img.save('testnumpyL16.png') | |
# === Command Line Support === | |
def _dehex(s): | |
"""Liberally convert from hex string to binary string.""" | |
import re | |
import binascii | |
# Remove all non-hexadecimal digits | |
s = re.sub(r'[^a-fA-F\d]', '', s) | |
# binscii.unhexlify works in Python 2 and Python 3 (unlike | |
# thing.decode('hex')). | |
return binascii.unhexlify(strtobytes(s)) | |
def _enhex(s): | |
"""Convert from binary string (bytes) to hex string (str).""" | |
import binascii | |
return bytestostr(binascii.hexlify(s)) | |
# Copies of PngSuite test files taken | |
# from http://www.schaik.com/pngsuite/pngsuite_bas_png.html | |
# on 2009-02-19 by drj and converted to hex. | |
# Some of these are not actually in PngSuite (but maybe they should | |
# be?), they use the same naming scheme, but start with a capital | |
# letter. | |
_pngsuite = { | |
'basi0g01': _dehex(""" | |
89504e470d0a1a0a0000000d49484452000000200000002001000000012c0677 | |
cf0000000467414d41000186a031e8965f0000009049444154789c2d8d310ec2 | |
300c45dfc682c415187a00a42e197ab81e83b127e00c5639001363a580d8582c | |
65c910357c4b78b0bfbfdf4f70168c19e7acb970a3f2d1ded9695ce5bf5963df | |
d92aaf4c9fd927ea449e6487df5b9c36e799b91bdf082b4d4bd4014fe4014b01 | |
ab7a17aee694d28d328a2d63837a70451e1648702d9a9ff4a11d2f7a51aa21e5 | |
a18c7ffd0094e3511d661822f20000000049454e44ae426082 | |
"""), | |
'basi0g02': _dehex(""" | |
89504e470d0a1a0a0000000d49484452000000200000002002000000016ba60d | |
1f0000000467414d41000186a031e8965f0000005149444154789c635062e860 | |
00e17286bb609c93c370ec189494960631366e4467b3ae675dcf10f521ea0303 | |
90c1ca006444e11643482064114a4852c710baea3f18c31918020c30410403a6 | |
0ac1a09239009c52804d85b6d97d0000000049454e44ae426082 | |
"""), | |
'basi0g04': _dehex(""" | |
89504e470d0a1a0a0000000d4948445200000020000000200400000001e4e6f8 | |
bf0000000467414d41000186a031e8965f000000ae49444154789c658e5111c2 | |
301044171c141c141c041c843a287510ea20d441c041c141c141c04191102454 | |
03994998cecd7edcecedbb9bdbc3b2c2b6457545fbc4bac1be437347f7c66a77 | |
3c23d60db15e88f5c5627338a5416c2e691a9b475a89cd27eda12895ae8dfdab | |
43d61e590764f5c83a226b40d669bec307f93247701687723abf31ff83a2284b | |
a5b4ae6b63ac6520ad730ca4ed7b06d20e030369bd6720ed383290360406d24e | |
13811f2781eba9d34d07160000000049454e44ae426082 | |
"""), | |
'basi0g08': _dehex(""" | |
89504e470d0a1a0a0000000d4948445200000020000000200800000001211615 | |
be0000000467414d41000186a031e8965f000000b549444154789cb5905d0ac2 | |
3010849dbac81c42c47bf843cf253e8878b0aa17110f214bdca6be240f5d21a5 | |
94ced3e49bcd322c1624115515154998aa424822a82a5624a1aa8a8b24c58f99 | |
999908130989a04a00d76c2c09e76cf21adcb209393a6553577da17140a2c59e | |
70ecbfa388dff1f03b82fb82bd07f05f7cb13f80bb07ad2fd60c011c3c588eef | |
f1f4e03bbec7ce832dca927aea005e431b625796345307b019c845e6bfc3bb98 | |
769d84f9efb02ea6c00f9bb9ff45e81f9f280000000049454e44ae426082 | |
"""), | |
'basi0g16': _dehex(""" | |
89504e470d0a1a0a0000000d49484452000000200000002010000000017186c9 | |
fd0000000467414d41000186a031e8965f000000e249444154789cb5913b0ec2 | |
301044c7490aa8f85d81c3e4301c8f53a4ca0da8902c8144b3920b4043111282 | |
23bc4956681a6bf5fc3c5a3ba0448912d91a4de2c38dd8e380231eede4c4f7a1 | |
4677700bec7bd9b1d344689315a3418d1a6efbe5b8305ba01f8ff4808c063e26 | |
c60d5c81edcf6c58c535e252839e93801b15c0a70d810ae0d306b205dc32b187 | |
272b64057e4720ff0502154034831520154034c3df81400510cdf0015c86e5cc | |
5c79c639fddba9dcb5456b51d7980eb52d8e7d7fa620a75120d6064641a05120 | |
b606771a05626b401a05f1f589827cf0fe44c1f0bae0055698ee8914fffffe00 | |
00000049454e44ae426082 | |
"""), | |
'basi2c08': _dehex(""" | |
89504e470d0a1a0a0000000d49484452000000200000002008020000018b1fdd | |
350000000467414d41000186a031e8965f000000f249444154789cd59341aa04 | |
210c44abc07b78133d59d37333bd89d76868b566d10cf4675af8596431a11662 | |
7c5688919280e312257dd6a0a4cf1a01008ee312a5f3c69c37e6fcc3f47e6776 | |
a07f8bdaf5b40feed2d33e025e2ff4fe2d4a63e1a16d91180b736d8bc45854c5 | |
6d951863f4a7e0b66dcf09a900f3ffa2948d4091e53ca86c048a64390f662b50 | |
4a999660ced906182b9a01a8be00a56404a6ede182b1223b4025e32c4de34304 | |
63457680c93aada6c99b73865aab2fc094920d901a203f5ddfe1970d28456783 | |
26cffbafeffcd30654f46d119be4793f827387fc0d189d5bc4d69a3c23d45a7f | |
db803146578337df4d0a3121fc3d330000000049454e44ae426082 | |
"""), | |
'basi2c16': _dehex(""" | |
89504e470d0a1a0a0000000d4948445200000020000000201002000001db8f01 | |
760000000467414d41000186a031e8965f0000020a49444154789cd5962173e3 | |
3010853fcf1838cc61a1818185a53e56787fa13fa130852e3b5878b4b0b03081 | |
b97f7030070b53e6b057a0a8912bbb9163b9f109ececbc59bd7dcf2b45492409 | |
d66f00eb1dd83cb5497d65456aeb8e1040913b3b2c04504c936dd5a9c7e2c6eb | |
b1b8f17a58e8d043da56f06f0f9f62e5217b6ba3a1b76f6c9e99e8696a2a72e2 | |
c4fb1e4d452e92ec9652b807486d12b6669be00db38d9114b0c1961e375461a5 | |
5f76682a85c367ad6f682ff53a9c2a353191764b78bb07d8ddc3c97c1950f391 | |
6745c7b9852c73c2f212605a466a502705c8338069c8b9e84efab941eb393a97 | |
d4c9fd63148314209f1c1d3434e847ead6380de291d6f26a25c1ebb5047f5f24 | |
d85c49f0f22cc1d34282c72709cab90477bf25b89d49f0f351822297e0ea9704 | |
f34c82bc94002448ede51866e5656aef5d7c6a385cb4d80e6a538ceba04e6df2 | |
480e9aa84ddedb413bb5c97b3838456df2d4fec2c7a706983e7474d085fae820 | |
a841776a83073838973ac0413fea2f1dc4a06e71108fda73109bdae48954ad60 | |
bf867aac3ce44c7c1589a711cf8a81df9b219679d96d1cec3d8bbbeaa2012626 | |
df8c7802eda201b2d2e0239b409868171fc104ba8b76f10b4da09f6817ffc609 | |
c413ede267fd1fbab46880c90f80eccf0013185eb48b47ba03df2bdaadef3181 | |
cb8976f18e13188768170f98c0f844bb78cb04c62ddac59d09fc3fa25dfc1da4 | |
14deb3df1344f70000000049454e44ae426082 | |
"""), | |
'basi3p08': _dehex(""" | |
89504e470d0a1a0a0000000d494844520000002000000020080300000133a3ba | |
500000000467414d41000186a031e8965f00000300504c5445224400f5ffed77 | |
ff77cbffff110a003a77002222ffff11ff110000222200ffac5566ff66ff6666 | |
ff01ff221200dcffffccff994444ff005555220000cbcbff44440055ff55cbcb | |
00331a00ffecdcedffffe4ffcbffdcdc44ff446666ff330000442200ededff66 | |
6600ffa444ffffaaeded0000cbcbfefffffdfffeffff0133ff33552a000101ff | |
8888ff00aaaa010100440000888800ffe4cbba5b0022ff22663200ffff99aaaa | |
ff550000aaaa00cb630011ff11d4ffaa773a00ff4444dc6b0066000001ff0188 | |
4200ecffdc6bdc00ffdcba00333300ed00ed7300ffff88994a0011ffff770000 | |
ff8301ffbabafe7b00fffeff00cb00ff999922ffff880000ffff77008888ffdc | |
ff1a33000000aa33ffff009900990000000001326600ffbaff44ffffffaaff00 | |
770000fefeaa00004a9900ffff66ff22220000998bff1155ffffff0101ff88ff | |
005500001111fffffefffdfea4ff4466ffffff66ff003300ffff55ff77770000 | |
88ff44ff00110077ffff006666ffffed000100fff5ed1111ffffff44ff22ffff | |
eded11110088ffff00007793ff2200dcdc3333fffe00febabaff99ffff333300 | |
63cb00baba00acff55ffffdcffff337bfe00ed00ed5555ffaaffffdcdcff5555 | |
00000066dcdc00dc00dc83ff017777fffefeffffffcbff5555777700fefe00cb | |
00cb0000fe010200010000122200ffff220044449bff33ffd4aa0000559999ff | |
999900ba00ba2a5500ffcbcbb4ff66ff9b33ffffbaaa00aa42880053aa00ffaa | |
aa0000ed00babaffff1100fe00000044009999990099ffcc99ba000088008800 | |
dc00ff93220000dcfefffeaa5300770077020100cb0000000033ffedff00ba00 | |
ff3333edffedffc488bcff7700aa00660066002222dc0000ffcbffdcffdcff8b | |
110000cb00010155005500880000002201ffffcbffcbed0000ff88884400445b | |
ba00ffbc77ff99ff006600baffba00777773ed00fe00003300330000baff77ff | |
004400aaffaafffefe000011220022c4ff8800eded99ff99ff55ff002200ffb4 | |
661100110a1100ff1111dcffbabaffff88ff88010001ff33ffb98ed362000002 | |
a249444154789c65d0695c0b001806f03711a9904a94d24dac63292949e5a810 | |
d244588a14ca5161d1a1323973252242d62157d12ae498c8124d25ca3a11398a | |
16e55a3cdffab0ffe7f77d7fcff3528645349b584c3187824d9d19d4ec2e3523 | |
9eb0ae975cf8de02f2486d502191841b42967a1ad49e5ddc4265f69a899e26b5 | |
e9e468181baae3a71a41b95669da8df2ea3594c1b31046d7b17bfb86592e4cbe | |
d89b23e8db0af6304d756e60a8f4ad378bdc2552ae5948df1d35b52143141533 | |
33bbbbababebeb3b3bc9c9c9c6c6c0c0d7b7b535323225a5aa8a02024a4bedec | |
0a0a2a2bcdcd7d7cf2f3a9a9c9cdcdd8b8adcdd5b5ababa828298982824a4ab2 | |
b21212acadbdbc1414e2e24859b9a72730302f4f49292c4c57373c9c0a0b7372 | |
8c8c1c1c3a3a92936d6dfdfd293e3e26262a4a4eaea2424b4b5fbfbc9c323278 | |
3c0b0ba1303abaae8ecdeeed950d6669a9a7a7a141d4de9e9d5d5cdcd2229b94 | |
c572716132f97cb1d8db9bc3110864a39795d9db6b6a26267a7a9a98d4d6a6a7 | |
cb76090ef6f030354d4d75766e686030545464cb393a1a1ac6c68686eae8f8f9 | |
a9aa4644c8b66d6e1689dcdd2512a994cb35330b0991ad9f9b6b659596a6addd | |
d8282fafae5e5323fb8f41d01f76c22fd8061be01bfc041a0323e1002c81cd30 | |
0b9ec027a0c930014ec035580fc3e112bc069a0b53e11c0c8095f00176c163a0 | |
e5301baec06a580677600ddc05ba0f13e120bc81a770133ec355a017300d4ec2 | |
0c7800bbe1219c02fa08f3e13c1c85dbb00a2ec05ea0dff00a6ec15a98027360 | |
070c047a06d7e1085c84f1b014f6c03fa0b33018b6c0211801ebe018fc00da0a | |
6f61113c877eb01d4ec317a085700f26c130f80efbe132bc039a0733e106fc81 | |
f7f017f6c10aa0d1300a0ec374780943e1382c06fa0a9b60238c83473016cec0 | |
02f80f73fefe1072afc1e50000000049454e44ae426082 | |
"""), | |
'basi6a08': _dehex(""" | |
89504e470d0a1a0a0000000d4948445200000020000000200806000001047d4a | |
620000000467414d41000186a031e8965f0000012049444154789cc595414ec3 | |
3010459fa541b8bbb26641b8069b861e8b4d12c1c112c1452a710a2a65d840d5 | |
949041fc481ec98ae27c7f3f8d27e3e4648047600fec0d1f390fbbe2633a31e2 | |
9389e4e4ea7bfdbf3d9a6b800ab89f1bd6b553cfcbb0679e960563d72e0a9293 | |
b7337b9f988cc67f5f0e186d20e808042f1c97054e1309da40d02d7e27f92e03 | |
6cbfc64df0fc3117a6210a1b6ad1a00df21c1abcf2a01944c7101b0cb568a001 | |
909c9cf9e399cf3d8d9d4660a875405d9a60d000b05e2de55e25780b7a5268e0 | |
622118e2399aab063a815808462f1ab86890fc2e03e48bb109ded7d26ce4bf59 | |
0db91bac0050747fec5015ce80da0e5700281be533f0ce6d5900b59bcb00ea6d | |
200314cf801faab200ea752803a8d7a90c503a039f824a53f4694e7342000000 | |
0049454e44ae426082 | |
"""), | |
'basn0g01': _dehex(""" | |
89504e470d0a1a0a0000000d49484452000000200000002001000000005b0147 | |
590000000467414d41000186a031e8965f0000005b49444154789c2dccb10903 | |
300c05d1ebd204b24a200b7a346f90153c82c18d0a61450751f1e08a2faaead2 | |
a4846ccea9255306e753345712e211b221bf4b263d1b427325255e8bdab29e6f | |
6aca30692e9d29616ee96f3065f0bf1f1087492fd02f14c90000000049454e44 | |
ae426082 | |
"""), | |
'basn0g02': _dehex(""" | |
89504e470d0a1a0a0000000d49484452000000200000002002000000001ca13d | |
890000000467414d41000186a031e8965f0000001f49444154789c6360085df5 | |
1f8cf1308850c20053868f0133091f6390b90700bd497f818b0989a900000000 | |
49454e44ae426082 | |
"""), | |
# A version of basn0g04 dithered down to 3 bits. | |
'Basn0g03': _dehex(""" | |
89504e470d0a1a0a0000000d494844520000002000000020040000000093e1c8 | |
2900000001734249540371d88211000000fd49444154789c6d90d18906210c84 | |
c356f22356b2889588604301b112112b11d94a96bb495cf7fe87f32d996f2689 | |
44741cc658e39c0b118f883e1f63cc89dafbc04c0f619d7d898396c54b875517 | |
83f3a2e7ac09a2074430e7f497f00f1138a5444f82839c5206b1f51053cca968 | |
63258821e7f2b5438aac16fbecc052b646e709de45cf18996b29648508728612 | |
952ca606a73566d44612b876845e9a347084ea4868d2907ff06be4436c4b41a3 | |
a3e1774285614c5affb40dbd931a526619d9fa18e4c2be420858de1df0e69893 | |
a0e3e5523461be448561001042b7d4a15309ce2c57aef2ba89d1c13794a109d7 | |
b5880aa27744fc5c4aecb5e7bcef5fe528ec6293a930690000000049454e44ae | |
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25dfb49ed2ff63908e6adf27d6d0dda7638d4154d2778daca17f58e61297c129 | |
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00000049454e44ae426082 | |
"""), | |
} | |
def test_suite(options, args): | |
""" | |
Create a PNG test image and write the file to stdout. | |
""" | |
# Below is a big stack of test image generators. | |
# They're all really tiny, so PEP 8 rules are suspended. | |
def test_gradient_horizontal_lr(x, y): return x | |
def test_gradient_horizontal_rl(x, y): return 1-x | |
def test_gradient_vertical_tb(x, y): return y | |
def test_gradient_vertical_bt(x, y): return 1-y | |
def test_radial_tl(x, y): return max(1-math.sqrt(x*x+y*y), 0.0) | |
def test_radial_center(x, y): return test_radial_tl(x-0.5, y-0.5) | |
def test_radial_tr(x, y): return test_radial_tl(1-x, y) | |
def test_radial_bl(x, y): return test_radial_tl(x, 1-y) | |
def test_radial_br(x, y): return test_radial_tl(1-x, 1-y) | |
def test_stripe(x, n): return float(int(x*n) & 1) | |
def test_stripe_h_2(x, y): return test_stripe(x, 2) | |
def test_stripe_h_4(x, y): return test_stripe(x, 4) | |
def test_stripe_h_10(x, y): return test_stripe(x, 10) | |
def test_stripe_v_2(x, y): return test_stripe(y, 2) | |
def test_stripe_v_4(x, y): return test_stripe(y, 4) | |
def test_stripe_v_10(x, y): return test_stripe(y, 10) | |
def test_stripe_lr_10(x, y): return test_stripe(x+y, 10) | |
def test_stripe_rl_10(x, y): return test_stripe(1+x-y, 10) | |
def test_checker(x, y, n): return float((int(x*n) & 1) ^ (int(y*n) & 1)) | |
def test_checker_8(x, y): return test_checker(x, y, 8) | |
def test_checker_15(x, y): return test_checker(x, y, 15) | |
def test_zero(x, y): return 0 | |
def test_one(x, y): return 1 | |
test_patterns = { | |
'GLR': test_gradient_horizontal_lr, | |
'GRL': test_gradient_horizontal_rl, | |
'GTB': test_gradient_vertical_tb, | |
'GBT': test_gradient_vertical_bt, | |
'RTL': test_radial_tl, | |
'RTR': test_radial_tr, | |
'RBL': test_radial_bl, | |
'RBR': test_radial_br, | |
'RCTR': test_radial_center, | |
'HS2': test_stripe_h_2, | |
'HS4': test_stripe_h_4, | |
'HS10': test_stripe_h_10, | |
'VS2': test_stripe_v_2, | |
'VS4': test_stripe_v_4, | |
'VS10': test_stripe_v_10, | |
'LRS': test_stripe_lr_10, | |
'RLS': test_stripe_rl_10, | |
'CK8': test_checker_8, | |
'CK15': test_checker_15, | |
'ZERO': test_zero, | |
'ONE': test_one, | |
} | |
def test_pattern(width, height, bitdepth, pattern): | |
"""Create a single plane (monochrome) test pattern. Returns a | |
flat row flat pixel array. | |
""" | |
maxval = 2**bitdepth-1 | |
if maxval > 255: | |
a = array('H') | |
else: | |
a = array('B') | |
fw = float(width) | |
fh = float(height) | |
pfun = test_patterns[pattern] | |
for y in range(height): | |
fy = float(y)/fh | |
for x in range(width): | |
a.append(int(round(pfun(float(x)/fw, fy) * maxval))) | |
return a | |
def test_rgba(size=256, bitdepth=8, | |
red="GTB", green="GLR", blue="RTL", alpha=None): | |
""" | |
Create a test image. Each channel is generated from the | |
specified pattern; any channel apart from red can be set to | |
None, which will cause it not to be in the image. It | |
is possible to create all PNG channel types (L, RGB, LA, RGBA), | |
as well as non PNG channel types (RGA, and so on). | |
""" | |
i = test_pattern(size, size, bitdepth, red) | |
psize = 1 | |
for channel in (green, blue, alpha): | |
if channel: | |
c = test_pattern(size, size, bitdepth, channel) | |
i = interleave_planes(i, c, psize, 1) | |
psize += 1 | |
return i | |
def pngsuite_image(name): | |
""" | |
Create a test image by reading an internal copy of the files | |
from the PngSuite. Returned in flat row flat pixel format. | |
""" | |
if name not in _pngsuite: | |
raise NotImplementedError("cannot find PngSuite file %s (use -L for a list)" % name) | |
r = Reader(bytes=_pngsuite[name]) | |
w,h,pixels,meta = r.asDirect() | |
assert w == h | |
# LAn for n < 8 is a special case for which we need to rescale | |
# the data. | |
if meta['greyscale'] and meta['alpha'] and meta['bitdepth'] < 8: | |
factor = 255 // (2**meta['bitdepth']-1) | |
def rescale(data): | |
for row in data: | |
yield list(map(factor.__mul__, row)) | |
pixels = rescale(pixels) | |
meta['bitdepth'] = 8 | |
arraycode = 'BH'[meta['bitdepth']>8] | |
return w, array(arraycode, itertools.chain(*pixels)), meta | |
# The body of test_suite() | |
size = 256 | |
if options.test_size: | |
size = options.test_size | |
options.bitdepth = options.test_depth | |
options.greyscale=bool(options.test_black) | |
kwargs = {} | |
if options.test_red: | |
kwargs["red"] = options.test_red | |
if options.test_green: | |
kwargs["green"] = options.test_green | |
if options.test_blue: | |
kwargs["blue"] = options.test_blue | |
if options.test_alpha: | |
kwargs["alpha"] = options.test_alpha | |
if options.greyscale: | |
if options.test_red or options.test_green or options.test_blue: | |
raise ValueError("cannot specify colours (R, G, B) when greyscale image (black channel, K) is specified") | |
kwargs["red"] = options.test_black | |
kwargs["green"] = None | |
kwargs["blue"] = None | |
options.alpha = bool(options.test_alpha) | |
if not args: | |
pixels = test_rgba(size, options.bitdepth, **kwargs) | |
else: | |
size,pixels,meta = pngsuite_image(args[0]) | |
for k in ['bitdepth', 'alpha', 'greyscale']: | |
setattr(options, k, meta[k]) | |
writer = Writer(size, size, | |
bitdepth=options.bitdepth, | |
transparent=options.transparent, | |
background=options.background, | |
gamma=options.gamma, | |
greyscale=options.greyscale, | |
alpha=options.alpha, | |
compression=options.compression, | |
interlace=options.interlace) | |
writer.write_array(sys.stdout, pixels) | |
def read_pam_header(infile): | |
""" | |
Read (the rest of a) PAM header. `infile` should be positioned | |
immediately after the initial 'P7' line (at the beginning of the | |
second line). Returns are as for `read_pnm_header`. | |
""" | |
# Unlike PBM, PGM, and PPM, we can read the header a line at a time. | |
header = dict() | |
while True: | |
l = infile.readline().strip() | |
if l == strtobytes('ENDHDR'): | |
break | |
if not l: | |
raise EOFError('PAM ended prematurely') | |
if l[0] == strtobytes('#'): | |
continue | |
l = l.split(None, 1) | |
if l[0] not in header: | |
header[l[0]] = l[1] | |
else: | |
header[l[0]] += strtobytes(' ') + l[1] | |
required = ['WIDTH', 'HEIGHT', 'DEPTH', 'MAXVAL'] | |
required = [strtobytes(x) for x in required] | |
WIDTH,HEIGHT,DEPTH,MAXVAL = required | |
present = [x for x in required if x in header] | |
if len(present) != len(required): | |
raise Error('PAM file must specify WIDTH, HEIGHT, DEPTH, and MAXVAL') | |
width = int(header[WIDTH]) | |
height = int(header[HEIGHT]) | |
depth = int(header[DEPTH]) | |
maxval = int(header[MAXVAL]) | |
if (width <= 0 or | |
height <= 0 or | |
depth <= 0 or | |
maxval <= 0): | |
raise Error( | |
'WIDTH, HEIGHT, DEPTH, MAXVAL must all be positive integers') | |
return 'P7', width, height, depth, maxval | |
def read_pnm_header(infile, supported=('P5','P6')): | |
""" | |
Read a PNM header, returning (format,width,height,depth,maxval). | |
`width` and `height` are in pixels. `depth` is the number of | |
channels in the image; for PBM and PGM it is synthesized as 1, for | |
PPM as 3; for PAM images it is read from the header. `maxval` is | |
synthesized (as 1) for PBM images. | |
""" | |
# Generally, see http://netpbm.sourceforge.net/doc/ppm.html | |
# and http://netpbm.sourceforge.net/doc/pam.html | |
supported = [strtobytes(x) for x in supported] | |
# Technically 'P7' must be followed by a newline, so by using | |
# rstrip() we are being liberal in what we accept. I think this | |
# is acceptable. | |
type = infile.read(3).rstrip() | |
if type not in supported: | |
raise NotImplementedError('file format %s not supported' % type) | |
if type == strtobytes('P7'): | |
# PAM header parsing is completely different. | |
return read_pam_header(infile) | |
# Expected number of tokens in header (3 for P4, 4 for P6) | |
expected = 4 | |
pbm = ('P1', 'P4') | |
if type in pbm: | |
expected = 3 | |
header = [type] | |
# We have to read the rest of the header byte by byte because the | |
# final whitespace character (immediately following the MAXVAL in | |
# the case of P6) may not be a newline. Of course all PNM files in | |
# the wild use a newline at this point, so it's tempting to use | |
# readline; but it would be wrong. | |
def getc(): | |
c = infile.read(1) | |
if not c: | |
raise Error('premature EOF reading PNM header') | |
return c | |
c = getc() | |
while True: | |
# Skip whitespace that precedes a token. | |
while c.isspace(): | |
c = getc() | |
# Skip comments. | |
while c == '#': | |
while c not in '\n\r': | |
c = getc() | |
if not c.isdigit(): | |
raise Error('unexpected character %s found in header' % c) | |
# According to the specification it is legal to have comments | |
# that appear in the middle of a token. | |
# This is bonkers; I've never seen it; and it's a bit awkward to | |
# code good lexers in Python (no goto). So we break on such | |
# cases. | |
token = strtobytes('') | |
while c.isdigit(): | |
token += c | |
c = getc() | |
# Slight hack. All "tokens" are decimal integers, so convert | |
# them here. | |
header.append(int(token)) | |
if len(header) == expected: | |
break | |
# Skip comments (again) | |
while c == '#': | |
while c not in '\n\r': | |
c = getc() | |
if not c.isspace(): | |
raise Error('expected header to end with whitespace, not %s' % c) | |
if type in pbm: | |
# synthesize a MAXVAL | |
header.append(1) | |
depth = (1,3)[type == strtobytes('P6')] | |
return header[0], header[1], header[2], depth, header[3] | |
def write_pnm(file, width, height, pixels, meta): | |
"""Write a Netpbm PNM/PAM file.""" | |
bitdepth = meta['bitdepth'] | |
maxval = 2**bitdepth - 1 | |
# Rudely, the number of image planes can be used to determine | |
# whether we are L (PGM), LA (PAM), RGB (PPM), or RGBA (PAM). | |
planes = meta['planes'] | |
# Can be an assert as long as we assume that pixels and meta came | |
# from a PNG file. | |
assert planes in (1,2,3,4) | |
if planes in (1,3): | |
if 1 == planes: | |
# PGM | |
# Could generate PBM if maxval is 1, but we don't (for one | |
# thing, we'd have to convert the data, not just blat it | |
# out). | |
fmt = 'P5' | |
else: | |
# PPM | |
fmt = 'P6' | |
file.write('%s %d %d %d\n' % (fmt, width, height, maxval)) | |
if planes in (2,4): | |
# PAM | |
# See http://netpbm.sourceforge.net/doc/pam.html | |
if 2 == planes: | |
tupltype = 'GRAYSCALE_ALPHA' | |
else: | |
tupltype = 'RGB_ALPHA' | |
file.write('P7\nWIDTH %d\nHEIGHT %d\nDEPTH %d\nMAXVAL %d\n' | |
'TUPLTYPE %s\nENDHDR\n' % | |
(width, height, planes, maxval, tupltype)) | |
# Values per row | |
vpr = planes * width | |
# struct format | |
fmt = '>%d' % vpr | |
if maxval > 0xff: | |
fmt = fmt + 'H' | |
else: | |
fmt = fmt + 'B' | |
for row in pixels: | |
file.write(struct.pack(fmt, *row)) | |
file.flush() | |
def color_triple(color): | |
""" | |
Convert a command line colour value to a RGB triple of integers. | |
FIXME: Somewhere we need support for greyscale backgrounds etc. | |
""" | |
if color.startswith('#') and len(color) == 4: | |
return (int(color[1], 16), | |
int(color[2], 16), | |
int(color[3], 16)) | |
if color.startswith('#') and len(color) == 7: | |
return (int(color[1:3], 16), | |
int(color[3:5], 16), | |
int(color[5:7], 16)) | |
elif color.startswith('#') and len(color) == 13: | |
return (int(color[1:5], 16), | |
int(color[5:9], 16), | |
int(color[9:13], 16)) | |
def _main(argv): | |
""" | |
Run the PNG encoder with options from the command line. | |
""" | |
# Parse command line arguments | |
from optparse import OptionParser | |
import re | |
version = '%prog ' + re.sub(r'( ?\$|URL: |Rev:)', '', __version__) | |
parser = OptionParser(version=version) | |
parser.set_usage("%prog [options] [imagefile]") | |
parser.add_option('-r', '--read-png', default=False, | |
action='store_true', | |
help='Read PNG, write PNM') | |
parser.add_option("-i", "--interlace", | |
default=False, action="store_true", | |
help="create an interlaced PNG file (Adam7)") | |
parser.add_option("-t", "--transparent", | |
action="store", type="string", metavar="color", | |
help="mark the specified colour (#RRGGBB) as transparent") | |
parser.add_option("-b", "--background", | |
action="store", type="string", metavar="color", | |
help="save the specified background colour") | |
parser.add_option("-a", "--alpha", | |
action="store", type="string", metavar="pgmfile", | |
help="alpha channel transparency (RGBA)") | |
parser.add_option("-g", "--gamma", | |
action="store", type="float", metavar="value", | |
help="save the specified gamma value") | |
parser.add_option("-c", "--compression", | |
action="store", type="int", metavar="level", | |
help="zlib compression level (0-9)") | |
parser.add_option("-T", "--test", | |
default=False, action="store_true", | |
help="create a test image (a named PngSuite image if an argument is supplied)") | |
parser.add_option('-L', '--list', | |
default=False, action='store_true', | |
help="print list of named test images") | |
parser.add_option("-R", "--test-red", | |
action="store", type="string", metavar="pattern", | |
help="test pattern for the red image layer") | |
parser.add_option("-G", "--test-green", | |
action="store", type="string", metavar="pattern", | |
help="test pattern for the green image layer") | |
parser.add_option("-B", "--test-blue", | |
action="store", type="string", metavar="pattern", | |
help="test pattern for the blue image layer") | |
parser.add_option("-A", "--test-alpha", | |
action="store", type="string", metavar="pattern", | |
help="test pattern for the alpha image layer") | |
parser.add_option("-K", "--test-black", | |
action="store", type="string", metavar="pattern", | |
help="test pattern for greyscale image") | |
parser.add_option("-d", "--test-depth", | |
default=8, action="store", type="int", | |
metavar='NBITS', | |
help="create test PNGs that are NBITS bits per channel") | |
parser.add_option("-S", "--test-size", | |
action="store", type="int", metavar="size", | |
help="width and height of the test image") | |
(options, args) = parser.parse_args(args=argv[1:]) | |
# Convert options | |
if options.transparent is not None: | |
options.transparent = color_triple(options.transparent) | |
if options.background is not None: | |
options.background = color_triple(options.background) | |
if options.list: | |
names = list(_pngsuite) | |
names.sort() | |
for name in names: | |
print(name) | |
return | |
# Run regression tests | |
if options.test: | |
return test_suite(options, args) | |
# Prepare input and output files | |
if len(args) == 0: | |
infilename = '-' | |
infile = sys.stdin | |
elif len(args) == 1: | |
infilename = args[0] | |
infile = open(infilename, 'rb') | |
else: | |
parser.error("more than one input file") | |
outfile = sys.stdout | |
if options.read_png: | |
# Encode PNG to PPM | |
png = Reader(file=infile) | |
width,height,pixels,meta = png.asDirect() | |
write_pnm(outfile, width, height, pixels, meta) | |
else: | |
# Encode PNM to PNG | |
format, width, height, depth, maxval = \ | |
read_pnm_header(infile, ('P5','P6','P7')) | |
# When it comes to the variety of input formats, we do something | |
# rather rude. Observe that L, LA, RGB, RGBA are the 4 colour | |
# types supported by PNG and that they correspond to 1, 2, 3, 4 | |
# channels respectively. So we use the number of channels in | |
# the source image to determine which one we have. We do not | |
# care about TUPLTYPE. | |
greyscale = depth <= 2 | |
pamalpha = depth in (2,4) | |
supported = [2**x-1 for x in range(1,17)] | |
try: | |
mi = supported.index(maxval) | |
except ValueError: | |
raise NotImplementedError( | |
'your maxval (%s) not in supported list %s' % | |
(maxval, str(supported))) | |
bitdepth = mi+1 | |
writer = Writer(width, height, | |
greyscale=greyscale, | |
bitdepth=bitdepth, | |
interlace=options.interlace, | |
transparent=options.transparent, | |
background=options.background, | |
alpha=bool(pamalpha or options.alpha), | |
gamma=options.gamma, | |
compression=options.compression) | |
if options.alpha: | |
pgmfile = open(options.alpha, 'rb') | |
format, awidth, aheight, adepth, amaxval = \ | |
read_pnm_header(pgmfile, 'P5') | |
if amaxval != '255': | |
raise NotImplementedError( | |
'maxval %s not supported for alpha channel' % amaxval) | |
if (awidth, aheight) != (width, height): | |
raise ValueError("alpha channel image size mismatch" | |
" (%s has %sx%s but %s has %sx%s)" | |
% (infilename, width, height, | |
options.alpha, awidth, aheight)) | |
writer.convert_ppm_and_pgm(infile, pgmfile, outfile) | |
else: | |
writer.convert_pnm(infile, outfile) | |
if __name__ == '__main__': | |
try: | |
_main(sys.argv) | |
except Error as e: | |
print(e, file=sys.stderr) |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#!/usr/bin/env python3 | |
""" | |
Python script to decode many (but at this time not all) of the *.sqi images in | |
a city building game | |
== Usage == | |
Invoke python3 sqi2png.py <file-name> [output file] | |
if output file is not specified it will be placed in <file-name>.png | |
Input file name ought to be *.sqi or *.sqi2 | |
== Requirements == | |
python3.x (tested on Python 3.2.3) | |
blist module for python (https://pypi.python.org/pypi/blist/) | |
python3 patched version of Johann C. Rocholl png module (ought to be included) | |
== LICENSE == | |
This software is in the public domain, furnished "as is", without technical | |
support, and with no warranty, express or implied, as to its usefulness for | |
any purpose. | |
sqi2png.py | |
Convery sqi to png images | |
""" | |
import blist | |
import io | |
import png | |
import sys | |
import zlib | |
def main(*argv): | |
"""C-ish style main entry for the program""" | |
if(len(argv) not in (2,3)): | |
print("usage: " + argv[0] + " <filename> [output file]") | |
return -1 | |
filenm=argv[1] | |
if(len(argv)==3): | |
outfile=argv[2] | |
else: | |
outfile=filenm + ".png" | |
print("checking file: " + filenm) | |
fp=open(filenm,"rb") | |
ftype=fp.read(4) | |
if(ftype != b"SQim"): | |
print("file type is unknown.. expected SQim") | |
return(-2) | |
fmt=fp.read(2) | |
width=fp.read(2) | |
width=(width[1]<<8) + width[0] | |
height=fp.read(2) | |
height=(height[1]<<8) + height[0] | |
print("width: " + str(width)) | |
print("height: " + str(height)) | |
datlen=fp.read(4) | |
datlen=(datlen[3]<<24)+(datlen[2]<<16)+(datlen[1]<<8)+datlen[0] | |
print("datlen: " + str(datlen)) | |
#read the file data | |
dat=fp.read(datlen) | |
if(fmt == b"g\x10"): | |
print("zlib compressed") | |
dat=zlib.decompress(dat) | |
elif(fmt == b"gP"): | |
print("zlib compressed (mini-image)") | |
dat=zlib.decompress(dat) | |
elif(fmt == b"g\x12"): | |
print("zlib 24bit solid image") | |
dat24b=io.BytesIO(zlib.decompress(dat)) | |
dat=io.BytesIO() | |
px=dat24b.read(3) | |
while(len(px)==3): | |
dat.write(px + b"\xff") | |
px=dat24b.read(3) | |
del(dat24b) | |
dat=dat.getvalue() | |
elif(fmt == b"g\x11"): | |
print("zlib 16bit animation") | |
#open("/tmp/16bitdump","wb").write(zlib.decompress(dat)) | |
dat16b=io.BytesIO(zlib.decompress(dat)) | |
dat=io.BytesIO() | |
pair=dat16b.read(2) | |
while(pair != b""): | |
#convert pixel data 16b->32b | |
pair = (pair[0]<<8)+(pair[1]) | |
blue = (((pair >> 12)&0xf)*0xff)//0xf | |
alpha = (((pair >> 8)&0xf)*0xff)//0xf | |
red = (((pair >> 4)&0xf)*0xff)//0xf | |
green = (((pair >> 0)&0xf)*0xff)//0xf | |
dat.write(bytes((red,green,blue,alpha))) | |
pair=dat16b.read(2) | |
#done converting get the raw 32b image data | |
pair=None | |
dat=dat.getvalue() | |
elif(fmt[1] == 0x10): | |
print("unknown file format: " +str(bytes((comp[0],)))) | |
sys.exit(-1) | |
else: | |
print("unexpected format code: " + str(fmt)) | |
sys.exit(-2) | |
#init the empty (blist) raster | |
imap=genImageMap(width,height) | |
#run over the raster and populate the 32b 8-8-8-8 image | |
x=0 | |
y=0 | |
i=0 | |
for pt in getQuads(dat): | |
i+=1 | |
imap[y][x*4:(x+1)*4]=pt | |
x+=1 | |
if(x>=width): | |
y+=1 | |
x=0 | |
if(y>=height): | |
y=0 | |
#convert the raster to a png image | |
im=png.from_array(imap,mode="RGBA") | |
print("Saving file to: " + outfile) | |
#write the resulting file | |
im.save(outfile) | |
return 0 | |
def genImageMap(w,h): | |
"""make a matrix (raster) of R-G-B-A (w*4) blists | |
this will be used for the image data""" | |
row=blist.blist((0,0,0,0)) * w | |
r=blist.blist() | |
for i in range(h): | |
r.append(blist.blist(row)) | |
return r | |
def getQuads(dat): | |
"""a generator to return quads of bytes in a tuple from a byte string | |
or array""" | |
for i in range(0,len(dat)-3,4): | |
yield((dat[i],dat[i+1],dat[i+2],dat[i+3])) | |
#ENTRY | |
if(__name__=="__main__"): | |
sys.exit(main(*sys.argv)) |
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