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# This file is part of VISVIS. This file may be distributed
# seperately, but under the same license as VISVIS (LGPL).
# images2gif is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation, either version 3 of
# the License, or (at your option) any later version.
# images2gif is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# GNU Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with this program. If not, see
# <>.
# Copyright (C) 2009 Almar Klein
""" Module images2gif
Provides functionality for reading and writing animated GIF images.
Use writeGif to write a series of numpy arrays or PIL images as an
animated GIF. Use readGif to read an animated gif as a series of numpy
Many thanks to Ant1 for:
* noting the use of "palette=PIL.Image.ADAPTIVE", which significantly
improves the results.
* the modifications to save each image with its own palette, or optionally
the global palette (if its the same).
- based on gifmaker (in the scripts folder of the source distribution of PIL)
- based on gif file structure as provided by wikipedia
import PIL
from PIL import Image, ImageChops
from PIL.GifImagePlugin import getheader, getdata
except ImportError:
PIL = None
import numpy as np
except ImportError:
np = None
# getheader gives a 87a header and a color palette (two elements in a list).
# getdata()[0] gives the Image Descriptor up to (including) "LZW min code size".
# getdatas()[1:] is the image data itself in chuncks of 256 bytes (well
# technically the first byte says how many bytes follow, after which that
# amount (max 255) follows).
def intToBin(i):
""" Integer to two bytes """
# devide in two parts (bytes)
i1 = i % 256
i2 = int( i/256)
# make string (little endian)
return chr(i1) + chr(i2)
def getheaderAnim(im):
""" Animation header. To replace the getheader()[0] """
bb = "GIF89a"
bb += intToBin(im.size[0])
bb += intToBin(im.size[1])
bb += "\x87\x00\x00"
return bb
def getImageDescriptor(im):
""" Used for the local color table properties per image.
Otherwise global color table applies to all frames irrespective of
wether additional colours comes in play that require a redefined palette
Still a maximum of 256 color per frame, obviously.
Written by Ant1 on 2010-08-22
bb = '\x2C' # Image separator,
bb += intToBin( 0 ) # Left position
bb += intToBin( 0 ) # Top position
bb += intToBin( im.size[0] ) # image width
bb += intToBin( im.size[1] ) # image height
bb += '\x87' # packed field : local color table flag1, interlace0, sorted table0, reserved00, lct size111=7=2^(7+1)=256.
# LZW minimum size code now comes later, begining of [image data] blocks
return bb
def getAppExt(loops=float('inf')):
""" Application extention. Part that specifies amount of loops.
If loops is inf, it goes on infinitely.
if loops == 0:
bb = "" # application extension should not be used
# (the extension interprets zero loops
# to mean an infinite number of loops)
bb = "\x21\xFF\x0B" # application extension
bb += "NETSCAPE2.0"
bb += "\x03\x01"
if loops == float('inf'):
loops = 2**16-1
bb += intToBin(loops)
bb += '\x00' # end
return bb
def getGraphicsControlExt(duration=0.1):
""" Graphics Control Extension. A sort of header at the start of
each image. Specifies transparancy and duration. """
bb = '\x21\xF9\x04'
bb += '\x08' # no transparancy
bb += intToBin( int(duration*100) ) # in 100th of seconds
bb += '\x00' # no transparant color
bb += '\x00' # end
return bb
def _writeGifToFile(fp, images, durations, loops):
""" Given a set of images writes the bytes to the specified stream.
# Obtain palette for all images and count each occurance
palettes, occur = [], []
for im in images:
palettes.append( getheader(im)[1] )
for palette in palettes:
occur.append( palettes.count( palette ) )
# Select most-used palette as the global one (or first in case no max)
globalPalette = palettes[ occur.index(max(occur)) ]
# Init
frames = 0
firstFrame = True
for im, palette in zip(images, palettes):
if firstFrame:
# Write header
# Gather info
header = getheaderAnim(im)
appext = getAppExt(loops)
# Write
# Next frame is not the first
firstFrame = False
if True:
# Write palette and image data
# Gather info
data = getdata(im)
imdes, data = data[0], data[1:]
graphext = getGraphicsControlExt(durations[frames])
# Make image descriptor suitable for using 256 local color palette
lid = getImageDescriptor(im)
# Write local header
if palette != globalPalette:
# Use local color palette
fp.write(lid) # write suitable image descriptor
fp.write(palette) # write local color table
fp.write('\x08') # LZW minimum size code
# Use global color palette
fp.write(imdes) # write suitable image descriptor
# Write image data
for d in data:
# Prepare for next round
frames = frames + 1
fp.write(";") # end gif
return frames
## Exposed functions
def writeGif(filename, images, duration=0.1, loops=0, dither=1):
""" writeGif(filename, images, duration=0.1, loops=0, dither=1)
Write an animated gif from the specified images.
images should be a list of numpy arrays of PIL images.
Numpy images of type float should have pixels between 0 and 1.
Numpy images of other types are expected to have values between 0 and 255.
if PIL is None:
raise RuntimeError("Need PIL to write animated gif files.")
images2 = []
# convert to PIL
for im in images:
if isinstance(im,Image.Image):
images2.append( im.convert('P', palette=AD, dither=dither) )
elif np and isinstance(im, np.ndarray):
if im.dtype == np.uint8:
elif im.dtype in [np.float32, np.float64]:
im = (im*255).astype(np.uint8)
im = im.astype(np.uint8)
# convert
if len(im.shape)==3 and im.shape[2]==3:
im = Image.fromarray(im,'RGB').convert('P', palette=AD, dither=dither)
elif len(im.shape)==2:
im = Image.fromarray(im,'L').convert('P', palette=AD, dither=dither)
raise ValueError("Array has invalid shape to be an image.")
raise ValueError("Unknown image type.")
# check duration
if hasattr(duration, '__len__'):
if len(duration) == len(images2):
durations = [d for d in duration]
raise ValueError("len(duration) doesn't match amount of images.")
durations = [duration for im in images2]
# open file
fp = open(filename, 'wb')
# write
n = _writeGifToFile(fp, images2, durations, loops)
print n, 'frames written'
def readGif(filename):
# Check PIL
if PIL is None:
raise RuntimeError("Need PIL to read animated gif files.")
# Check whether it exists
if not os.path.isfile(filename):
raise IOError('File not found: '+str(filename))
# Load file using PIL
pilIm =
# Read all images inside
ims = []
while True:
# Get image as numpy array
tmp = pilIm.convert() # Make without palette
a = np.asarray(tmp)
if len(a.shape)==0:
raise MemoryError("Too little memory to convert PIL image to array")
# Store, and next
except EOFError:
# Done
return ims
if __name__ == '__main__':
im = np.zeros((200,200), dtype=np.uint8)
im[10:30,:] = 100
im[:,80:120] = 255
im[-50:-40,:] = 50
images = [im*1.0, im*0.8, im*0.6, im*0.4, im*0]
writeGif('lala3.gif',images, duration=0.5, dither=0)
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