Create png_fix and document its use
Remove png_check and png_make_srgb, and replace them with png_fix. It aggressively rebuilds png files by discarding chunks. Bug: 1289511 Change-Id: I3489e0d02ff9ffb58bd19fa48850c78b476fb701 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3422234 Auto-Submit: Avi Drissman <avi@chromium.org> Reviewed-by: Mark Mentovai <mark@chromium.org> Commit-Queue: Mark Mentovai <mark@chromium.org> Cr-Commit-Position: refs/heads/main@{#964776}
This commit is contained in:
Avi Drissman
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Chromium LUCI CQ
Chromium LUCI CQ
parent
73265ee7c7
commit
d899445d1d
@ -48,8 +48,7 @@ in PNG format: 16×16, 32×32, 128×128, 256×256, and 512×512, named `16.png`,
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1. Process the `.png` files with:
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1. `optipng -o7 -zm1-9`
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1. `advpng -z4 -i50`
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1. `png_make_srgb.py`
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1. `png_check.py`
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1. `png_fix.py`
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1. Create the `.icns` file with the `makeicns2` you compiled:
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`makeicns2 <name>.iconset`
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@ -1,65 +0,0 @@
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#!/usr/bin/env python
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# Copyright 2020 The Chromium Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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# Does a quick parse of a png file, to make sure that no unneeded png chunks are
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# present in the file.
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import struct
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import sys
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def verify(path):
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file = open(path, 'rb')
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magic = file.read(8)
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assert magic == b'\x89\x50\x4e\x47\x0d\x0a\x1a\x0a'
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color_type = None
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chunk_types = []
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while True:
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chunk_header = file.read(8)
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(chunk_length, chunk_type) = struct.unpack('>I4s', chunk_header)
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if chunk_type == b'IHDR':
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ihdr = file.read(chunk_length)
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(width, height, bit_depth, color_type, compression_method,
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filter_method, interlace_method) = struct.unpack('>2I5b', ihdr)
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else:
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file.seek(chunk_length, 1)
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chunk_footer = file.read(4)
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(chunk_crc,) = struct.unpack('>I', chunk_footer)
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chunk_types.append(chunk_type)
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if chunk_type == b'IEND':
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break
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# The only two color types that have transparency and can be used for icons
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# are types 3 (indexed) and 6 (direct RGBA).
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assert color_type in (3, 6), "Disallowed color type {}".format(color_type)
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allowed_chunk_types = [b'IHDR', b'sRGB', b'IDAT', b'IEND']
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if color_type == 3:
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allowed_chunk_types.extend([b'PLTE', b'tRNS'])
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for chunk_type in chunk_types:
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assert (chunk_type in allowed_chunk_types
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), "Disallowed chunk of type {}".format(chunk_type)
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eof = file.read(1)
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assert len(eof) == 0
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file.close()
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def main(args):
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for path in args:
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print(path)
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verify(path)
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return 0
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if __name__ == '__main__':
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sys.exit(main(sys.argv[1:]))
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120
tools/mac/icons/png_fix.py
Executable file
120
tools/mac/icons/png_fix.py
Executable file
@ -0,0 +1,120 @@
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#!/usr/bin/env python3
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# Copyright 2022 The Chromium Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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# Rebuilds PNG files intended for use as icon images on the Mac. It is
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# reasonably robust, but is not designed to be robust against adversarially-
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# constructed files.
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#
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# This is an opinionated script and makes assumptions about the desired
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# characteristics of a PNG file for use as a Mac icon. All users of this script
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# must verify that those are the correct assumptions for their use case before
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# using it.
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import argparse
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import binascii
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import os
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import struct
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import sys
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_PNG_MAGIC = b'\x89\x50\x4e\x47\x0d\x0a\x1a\x0a'
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_CHUNK_HEADER_STRUCT = struct.Struct('>I4s')
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_CHUNK_CRC_STRUCT = struct.Struct('>I')
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class FormatError(Exception):
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pass
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def _process_path(path):
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with open(path, 'r+b') as file:
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return _process_file(file)
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def _process_file(file):
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magic = file.read(len(_PNG_MAGIC))
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if magic != _PNG_MAGIC:
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raise FormatError(file, file.tell(), 'bad magic', magic, _PNG_MAGIC)
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chunks = {}
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while True:
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chunk_header = file.read(_CHUNK_HEADER_STRUCT.size)
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(chunk_length, chunk_type) = _CHUNK_HEADER_STRUCT.unpack(chunk_header)
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chunk = chunk_header + file.read(chunk_length + _CHUNK_CRC_STRUCT.size)
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if chunk_type in chunks:
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raise FormatError(file, file.tell(), 'duplicate chunk', chunk_type)
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chunks[chunk_type] = chunk
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if chunk_type == b'IEND':
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break
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eof = file.read(1)
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if len(eof) != 0:
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raise FormatError(file, '\'IEND\' chunk not at end')
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ihdr = chunks[b'IHDR'][_CHUNK_HEADER_STRUCT.size:-_CHUNK_CRC_STRUCT.size]
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(ihdr_width, ihdr_height, ihdr_bit_depth, ihdr_color_type,
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ihdr_compression_method, ihdr_filter_method,
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ihdr_interlace_method) = struct.unpack('>2I5b', ihdr)
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# The only two color types that have transparency and can be used for icons
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# are types 3 (indexed) and 6 (direct RGBA).
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if ihdr_color_type not in (3, 6):
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raise FormatError(file, 'disallowed color type', color_type)
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if ihdr_color_type == 3 and b'PLTE' not in chunks:
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raise FormatError(file, 'indexed color requires \'PLTE\' chunk')
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if ihdr_color_type == 3 and b'tRNS' not in chunks:
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raise FormatError(file, 'indexed color requires \'tRNS\' chunk')
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if b'IDAT' not in chunks:
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raise FormatError(file, 'missing \'IDAT\' chunk')
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if b'iCCP' in chunks:
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raise FormatError(file, 'disallowed color profile; sRGB only')
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if b'sRGB' not in chunks:
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# Note that a value of 0 is a perceptual rendering intent (e.g.
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# photographs) while a value of 1 is a relative colorimetric rendering
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# intent (e.g. icons). Every macOS icon that has an 'sRGB' chunk uses 0
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# so that is what is used here. Please forgive us, UX.
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#
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# Reference:
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# http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html#C.sRGB
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srgb_chunk_type = struct.pack('>4s', b'sRGB')
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srgb_chunk_data = struct.pack('>b', 0) # Perceptual
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srgb_chunk_length = struct.pack('>I', len(srgb_chunk_data))
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srgb_chunk_crc = struct.pack(
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'>I', binascii.crc32(srgb_chunk_type + srgb_chunk_data))
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chunks[b'sRGB'] = (
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srgb_chunk_length + srgb_chunk_type + srgb_chunk_data +
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srgb_chunk_crc)
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file.seek(len(_PNG_MAGIC), os.SEEK_SET)
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file.write(chunks[b'IHDR'])
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file.write(chunks[b'sRGB'])
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if ihdr_color_type == 3:
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file.write(chunks[b'PLTE'])
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file.write(chunks[b'tRNS'])
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file.write(chunks[b'IDAT'])
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file.write(chunks[b'IEND'])
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file.truncate()
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def main(args):
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parser = argparse.ArgumentParser()
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parser.add_argument('paths', nargs='+', metavar='path')
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parsed = parser.parse_args(args)
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for path in parsed.paths:
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print(path)
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_process_path(path)
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if __name__ == '__main__':
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sys.exit(main(sys.argv[1:]))
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@ -1,86 +0,0 @@
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#!/usr/bin/env python
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# Copyright 2020 The Chromium Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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# Adds an sRGB chunk to a png file if one isn't already there.
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#
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# This is quick and dirty. It doesn't check for iCCP or other chunks that might
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# conflict with the sRGB. Obviously, only use this if it's desirable for the
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# png file to be treated as sRGB.
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import binascii
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import struct
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import sys
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def make_srgb(path):
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file = open(path, 'r+b')
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magic = file.read(8)
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assert magic == b'\x89\x50\x4e\x47\x0d\x0a\x1a\x0a'
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found_ihdr = False
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after_ihdr = 0
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found_srgb = False
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while True:
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chunk_header = file.read(8)
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(chunk_length, chunk_type) = struct.unpack('>I4s', chunk_header)
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file.seek(chunk_length, 1)
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chunk_footer = file.read(4)
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(chunk_crc,) = struct.unpack('>I', chunk_footer)
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if chunk_type == b'IHDR':
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assert not found_ihdr
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found_ihdr = True
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after_ihdr = file.tell()
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else:
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assert found_ihdr
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if chunk_type == b'sRGB':
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assert not found_srgb
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found_srgb = True
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if chunk_type == b'IEND':
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break
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eof = file.read(1)
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assert len(eof) == 0
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if not found_srgb:
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file.seek(after_ihdr)
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remainder = file.read()
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file.seek(after_ihdr)
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# Note that a value of 0 is a perceptual rendering intent (e.g.
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# photographs) while a value of 1 is a relative colorimetric rendering
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# intent (e.g. icons). Every macOS icon that has an 'sRGB' chunk uses 0
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# so that is what is used here. Please forgive us, UX.
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#
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# Reference:
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# http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html#C.sRGB
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srgb_chunk_type = struct.pack('>4s', b'sRGB')
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srgb_chunk_data = struct.pack('>b', 0) # Perceptual
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srgb_chunk_length = struct.pack('>I', len(srgb_chunk_data))
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srgb_chunk_crc = struct.pack(
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'>I',
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binascii.crc32(srgb_chunk_type + srgb_chunk_data) & 0xffffffff)
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srgb_chunk = (
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srgb_chunk_length + srgb_chunk_type + srgb_chunk_data +
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srgb_chunk_crc)
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file.write(srgb_chunk)
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file.write(remainder)
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file.close()
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def main(args):
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for path in args:
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print(path)
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make_srgb(path)
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return 0
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if __name__ == '__main__':
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sys.exit(main(sys.argv[1:]))
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