<ImageHeader: 32x32>
<Background: #ffffff>
<Resolution: 72.01 dpi>
<ModificationTime: 2020-01-17 12:41:12>
<ImageData: IDAT (4139)>
<EndOfFile: IEND (0)>
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png_chunks.py
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| """ | |
| Reads PNG Chunk Data. | |
| http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html | |
| http://www.libpng.org/pub/png/spec/1.2/PNG-Compression.html | |
| """ | |
| import sys | |
| import datetime | |
| import pathlib | |
| import collections | |
| import zlib | |
| def big_endian_number(function): | |
| def convert_bytes(*args, **kwargs): | |
| return int.from_bytes(function(*args, **kwargs), 'big') | |
| return convert_bytes | |
| class _Chunk: | |
| class WrongLength(Exception): | |
| def __init__(self, actual_length, expected_length): | |
| self._actual_length = actual_length | |
| self._expected_length = expected_length | |
| def __str__(self): | |
| return ( | |
| f'Wrong amount of data read:\n' | |
| f' Length of data read: {self._actual_length}\n' | |
| f' Expected Length: {self._expected_length}\n' | |
| ) | |
| class ChecksumMismatch(Exception): | |
| def __init__(self, actual_crc, expected_crc): | |
| self._actual_crc = actual_crc | |
| self._expected_crc = expected_crc | |
| def __str__(self): | |
| return ( | |
| f'Data Corruption detected:\n' | |
| f' Actual: {self._actual_crc}\n' | |
| f' Expected: {self._expected_crc}\n' | |
| ) | |
| def __init__(self, length, chunk_type, data, crc): | |
| self._length = length | |
| self._chunk_type = chunk_type | |
| self._data = data | |
| self._crc = crc | |
| self._check_length() | |
| self._check_sum() | |
| def _check_length(self): | |
| if self._length == len(self._data): | |
| return | |
| raise Chunk.WrongLength( | |
| len(self._data), self._length | |
| ) | |
| def _check_sum(self): | |
| actual_crc = zlib.crc32(self._chunk_type + self._data) | |
| if actual_crc == self._crc: | |
| return | |
| raise Chunk.ChecksumMismatch( | |
| self._actual_crc, self._crc | |
| ) | |
| def __repr__(self): | |
| name = self.__class__.__name__ | |
| type_ = self._chunk_type.decode('ascii') | |
| return f'<{name}: {type_} ({self._length})>' | |
| class ImageHeader(_Chunk): | |
| def __init__(self, *args): | |
| super().__init__(*args) | |
| @big_endian_number | |
| def width(self): | |
| return self._data[:4] | |
| @big_endian_number | |
| def height(self): | |
| return self._data[4:8] | |
| @big_endian_number | |
| def bit_depth(self): | |
| return self._data[8:9] | |
| @big_endian_number | |
| def color_type(self): | |
| # IF 6, Pixels are RGB Triple and Bit Depth must be 8 or 16 | |
| return self._data[9:10] | |
| @big_endian_number | |
| def compression_method(self): | |
| # PNG 1.1: @0 | |
| return self._data[10:11] | |
| @big_endian_number | |
| def filter_method(self): | |
| # PNG 1.1: @0 | |
| return self._data[11:12] | |
| @big_endian_number | |
| def interlace_method(self): | |
| # 0 == no interlace | |
| # 1 == interlace | |
| return self._data[12:13] | |
| def __repr__(self): | |
| w, h = self.width(), self.height() | |
| return f'<ImageHeader: {w}x{h}>' | |
| class ImageData(_Chunk): | |
| def deflate(self): | |
| # Data is in zlib Format, thus comes with a header | |
| # (first couple of bytes) | |
| # and an ADLER32 CRC (last 4 bytes) | |
| # This could word off the shelf like this, but I haven't tried | |
| # return zlib.decompress(self._data) | |
| raise NotImplemented() | |
| class ModificationTime(_Chunk): | |
| ''' | |
| # Time of last Image Modification | |
| LEN: 00 00 00 07 (7) | |
| TYP: 74 49 4d 45 (tIME) | |
| DAT: | |
| - 07 e4 (YEAR) | |
| - 01 (MONTH) | |
| - 11 (DAY) | |
| - 0c (HOUR) | |
| - 29 (MINUTE) | |
| - 0c (SECOND) | |
| CRC: d0 2e c0 da (SUM) | |
| ''' | |
| def __repr__(self): | |
| yyyy = int.from_bytes(self._data[:2], 'big') | |
| month, day, hour, minute, second = self._data[2:] | |
| time = datetime.datetime(yyyy, month, day, hour, minute, second) | |
| return f'<ModificationTime: {time}>' | |
| class Background(_Chunk): | |
| ''' | |
| # Background Color | |
| LEN: 00 00 00 06 (6) | |
| TYP: 62 4b 47 44 (bKGD) | |
| DAT: | |
| - 00 ff (RED) | |
| - 00 ff (GREEN) | |
| - 00 ff (BLUE) | |
| CRC: a0 bd a7 93 (SUM) | |
| ''' | |
| @big_endian_number | |
| def red(self): | |
| return self._data[0:2] | |
| @big_endian_number | |
| def green(self): | |
| return self._data[2:4] | |
| @big_endian_number | |
| def blue(self): | |
| return self._data[4:6] | |
| def __repr__(self): | |
| rgb = (self.red(), self.green(), self.blue()) | |
| color = ''.join(f'{channel:02x}' for channel in rgb) | |
| return f'<Background: #{color}>' | |
| class Text(_Chunk): | |
| KEYWORDS = [ | |
| 'Title', 'Author', 'Description', 'Copyright', | |
| 'Creation Time', 'Software', 'Disclaimer', 'Warning', | |
| 'Source', 'Comment' | |
| ] | |
| def keyword(self): | |
| content = self._data[:80].decode('utf-8') | |
| for keyword in self.KEYWORDS: | |
| if content.startswith(keyword): | |
| return keyword | |
| return f'<Weird Keyword: {content}>' | |
| def text(self): | |
| keyword = self.keyword() | |
| return self._data[len(keyword):].decode('utf-8') | |
| def __repr__(self): | |
| return f'<Text: {self.keyword()}: "{self.text()}">' | |
| class PhysicalDimensions(_Chunk): | |
| # Resolution? | |
| ''' | |
| # Physical Pixel Dimensions | |
| LEN: 00 00 00 09 (9) | |
| TYP: 70 48 59 73 (pHYs) | |
| DAT: | |
| - 00 00 0b 13 (2835) [X Pixels per unit, i.e. 72.009 dpi] | |
| - 00 00 0b 13 (2835) [Y Pixels per unit, i.e. 72.009 dpi] | |
| - 01 (Unit) [0=?, 1=meter] | |
| CRC: 00 9a 9c 18 (SUM) | |
| ''' | |
| @big_endian_number | |
| def x_pixels_per_unit(self): | |
| return self._data[0:4] | |
| @big_endian_number | |
| def y_pixels_per_unit(self): | |
| return self._data[4:9] | |
| def __repr__(self): | |
| DPI_FACTOR = 0.0254 | |
| dpi = self.x_pixels_per_unit() * DPI_FACTOR | |
| return f'<Resolution: {dpi:.2f} dpi>' | |
| class UnknownChunk(_Chunk): | |
| ''' | |
| Null object. I haven't implemented all chunk types. | |
| The most important types are IHDR, IDAT, and IEND. | |
| - PLTE (Palette Information) | |
| Ancillary chunks (identifyable by their lowercase letter, as determined by | |
| bit 5 of the first byte) are: | |
| - tRNS (Transparency) | |
| - gAMA (Gamma Correction) | |
| - cHRM (Primary Chromaticities) | |
| - sRGB (Standard RGB Color Space) | |
| - iCCP (Embedded ICC Profile) | |
| - tEXt, iTXt, and zTXt (Text, International Text, Compressed Text) | |
| - sBIT (Significant bits) | |
| - sPLT (Palette) | |
| - hIST (Palette Histogram) | |
| See: http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html | |
| ''' | |
| pass | |
| class EndOfFile(_Chunk): | |
| pass | |
| class Chunk: | |
| CHUNK_TYPES = { | |
| b'IHDR': ImageHeader, | |
| b'IDAT': ImageData, | |
| b'IEND': EndOfFile, | |
| b'bKGD': Background, | |
| b'pHYs': PhysicalDimensions, | |
| b'tIME': ModificationTime, | |
| b'tEXt': Text, | |
| } | |
| def __new__(cls, length, chunk_type, data, crc): | |
| ChunkType = cls.CHUNK_TYPES.get(chunk_type, UnknownChunk) | |
| return ChunkType(length, chunk_type, data, crc) | |
| class Chunks: | |
| def __init__(self, file): | |
| self._file = file | |
| @big_endian_number | |
| def _read_number(self, n=1): | |
| bytes_ = self._file.read(4) | |
| if not bytes_: | |
| raise StopIteration | |
| return bytes_ | |
| def _write_number(self, number): | |
| # TODO: Maybe later... | |
| # To write, use this: | |
| # return number.to_bytes(4, byteorder='big') | |
| raise NotImplemented | |
| def _read_chunk_data(self): | |
| length = self._read_number(4) | |
| chunk_type = self._file.read(4) | |
| data = self._file.read(length) | |
| checksum = self._read_number(4) | |
| return length, chunk_type, data, checksum | |
| def __iter__(self): | |
| data = self._read_chunk_data() | |
| yield ImageHeader(*data) | |
| while True: | |
| data = self._read_chunk_data() | |
| yield Chunk(*data) | |
| class Signature: | |
| ''' | |
| The signature is built in such a way that printing the image to a | |
| terminal will not dump all data (on msdos type), hence the "portable"... | |
| SIG: 89 | |
| PNG: 50 4e 47 (PNG) | |
| BRK: 0d 0a 1a 0a (CR,LF,EOF,LF) | |
| ''' | |
| @classmethod | |
| def read(cls, file): | |
| # Signature | |
| assert file.read(1) == b'\x89' | |
| assert file.read(3) == b'PNG' | |
| # Break: CR,LF,EOF,LF | |
| assert file.read(4) == bytes([0x0d, 0x0a, 0x1a, 0x0a]) | |
| return cls() | |
| def print_chunks(file): | |
| Signature.read(file) | |
| for chunk in Chunks(file): | |
| print(chunk) | |
| if __name__ == '__main__': | |
| _, filename = sys.argv | |
| with open(filename, 'rb') as file: | |
| print_chunks(file) |
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| ## Annotated PNG file showing a 32x32 black and white checkers flag | |
| ## Annotated Image Header | |
| ## http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html | |
| ## http://www.libpng.org/pub/png/spec/1.2/PNG-Compression.html | |
| ## COOL, somebody did that: : https://parsiya.net/blog/2018-02-25-extracting-png-chunks-with-go/#idat-chunks | |
| # Signature | |
| SIG: 89 | |
| PNG: 50 4e 47 (PNG) | |
| BRK: 0d 0a 1a 0a (CR,LF,EOF,LF) | |
| # Image Header | |
| LEN: 00 00 00 0d (13) | |
| TYP: 49 48 44 52 (IHDR) | |
| DAT: | |
| - 00 00 00 20 (WIDTH, 32) | |
| - 00 00 00 20 (HEIGHT, 32) | |
| - 08 (BIT DEPTH) | |
| - 06 (COLOR TYPE) [Pixels are RGB Triple, Bit Depth must be 8 or 16] | |
| - 00 (COMPRESSION METHOD) [0, atm] | |
| - 00 (FILTER METHOD) [0, atm] | |
| - 00 (INTERLACE METHOD) [No Interlace] | |
| CRC: 73 7a 7af4 (SUM) | |
| # Background Color | |
| LEN: 00 00 00 06 (6) | |
| TYP: 62 4b 47 44 (bKGD) | |
| DAT: | |
| - 00 ff (RED) | |
| - 00 ff (GREEN) | |
| - 00 ff (BLUE) | |
| CRC: a0 bd a7 93 (SUM) | |
| # Physical Pixel Dimensions | |
| LEN: 00 00 00 09 (9) | |
| TYP: 70 48 59 73 (pHYs) | |
| DAT: | |
| - 00 00 0b 13 (2835) [X Pixels per unit, i.e. 72.009 dpi] | |
| - 00 00 0b 13 (2835) [Y Pixels per unit, i.e. 72.009 dpi] | |
| - 01 (Unit) [0=?, 1=meter] | |
| CRC: 00 9a 9c 18 (SUM) | |
| # Time of last Image Modification | |
| LEN: 00 00 00 07 (7) | |
| TYP: 74 49 4d 45 (tIME) | |
| DAT: | |
| - 07 e4 (YEAR) | |
| - 01 (MONTH) | |
| - 11 (DAY) | |
| - 0c (HOUR) | |
| - 29 (MINUTE) | |
| - 0c (SECOND) | |
| CRC: d0 2e c0 da (SUM) | |
| # Image Data, Multiple Possible | |
| LEN: 00 00 10 2b (4139) | |
| TYP: 49 44 41 54 (IDAT) | |
| DAT: (ZLIB FORMAT) | |
| # Filter Type Byte Per Scanline | |
| - 58 [88, ZLIB DEFLATE STUFF] | |
| - 09 [9, ZLIB DEFLATE STUFF] | |
| 01 20 | |
| 10 df ef 00ff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ff00 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 00ff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ff00 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 00ff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ff00 | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 00ff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ff00 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 00ff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ff00 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 00ff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ff00 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 00ff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ff00 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 00ff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ff00 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 00ff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ff00 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 00ff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ff00 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 00ff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ff00 | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 00ff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ff00 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 00ff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ffff ffff ff00 0000 ffff ffff ff00 | |
| 0000 ff00 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 0000 00ff ffff ffff 0000 00ff | |
| ffff ffff 00ff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ffff ffff ff00 0000 ffff ffff | |
| ff00 0000 ff00 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 0000 00ff ffff ffff 0000 | |
| 00ff ffff ffff 00ff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ffff ffff ff00 0000 ffff | |
| ffff ff00 0000 ff00 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 0000 00ff ffff ffff | |
| 0000 00ff ffff ffff 00ff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ffff ffff ff00 0000 | |
| ffff ffff ff00 0000 ff00 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff 0000 00ff ffff | |
| ffff 0000 00ff ffff ffff | |
| CHK: 27 df f6 88 (ADLER32, ZLIB CHECK) | |
| CRC: e9 75 90 8a (SUM) | |
| LEN: 00 00 00 00 (0) | |
| TYP: 49 45 4e 44 (IEND) | |
| CRC: ae 42 60 82 (SUM) | |
| ### CRC: TYP + DAT | |
| >>> import zlib | |
| >>> data = bytes([0x62, 0x4b, 0x47, 0x44, 0x00, 0xff, 0x00, 0xff, 0x00, 0xff]) | |
| >>> format(zlib.crc32(data), 'x') | |
| 'a0bda793' |
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| import sys | |
| class Chunk: | |
| def __init__(self, length, chunk_type, data, crc): | |
| self._length = length | |
| self._chunk_type = chunk_type | |
| self._data = data | |
| self._crc = crc | |
| def __repr__(self): | |
| name = self.__class__.__name__ | |
| type_ = self._chunk_type.decode('ascii') | |
| return f'<{name}: {type_} ({self._length})>' | |
| class Chunks: | |
| def __init__(self, file): | |
| self._file = file | |
| def _read_number(self, n=1): | |
| bytes_ = self._file.read(4) | |
| if not bytes_: | |
| raise StopIteration | |
| return int.from_bytes(bytes_, 'big') | |
| def __iter__(self): | |
| while True: | |
| length = self._read_number(4) | |
| chunk_type = self._file.read(4) | |
| data = self._file.read(length) | |
| checksum = self._read_number(4) | |
| yield Chunk(length, chunk_type, data, checksum) | |
| class Signature: | |
| @classmethod | |
| def read(cls, file): | |
| # Signature | |
| assert file.read(4) == b'\x89PNG' | |
| # Break: CR,LF,EOF,LF | |
| assert file.read(4) == bytes([0x0d, 0x0a, 0x1a, 0x0a]) | |
| if __name__ == '__main__': | |
| _, filename = sys.argv | |
| with open(filename, 'rb') as file: | |
| Signature.read(file) | |
| for chunk in Chunks(file): | |
| print(chunk) |
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