tools/resources/optimize-ico-files.py

   1 #!/usr/bin/env python
   2 # Copyright 2015 The Chromium Authors. All rights reserved.
   3 # Use of this source code is governed by a BSD-style license that can be
   4 # found in the LICENSE file.
   5
   6 """Windows ICO file crusher.
   7
   8 Optimizes the PNG images within a Windows ICO icon file. This extracts all of
   9 the sub-images within the file, runs any PNG-formatted images through
  10 optimize-png-files.sh, then packs them back into an ICO file.
  11
  12 NOTE: ICO files can contain both raw uncompressed BMP files and PNG files. This
  13 script does not touch the BMP files, which means if you have a huge uncompressed
  14 image, it will not get smaller. 256x256 icons should be PNG-formatted first.
  15 (Smaller icons should be BMPs for compatibility with Windows XP.)
  16 """
  17
  18 import argparse
  19 import logging
  20 import os
  21 import StringIO
  22 import struct
  23 import subprocess
  24 import sys
  25 import tempfile
  26
  27 OPTIMIZE_PNG_FILES = 'tools/resources/optimize-png-files.sh'
  28
  29 logging.basicConfig(level=logging.INFO, format='%(levelname)s: %(message)s')
  30
  31 class InvalidFile(Exception):
  32   """Represents an invalid ICO file."""
  33
  34 def IsPng(png_data):
  35   """Determines whether a sequence of bytes is a PNG."""
  36   return png_data.startswith('\x89PNG\r\n\x1a\n')
  37
  38 def OptimizePngFile(temp_dir, png_filename, optimization_level=None):
  39   """Optimize a PNG file.
  40
  41   Args:
  42     temp_dir: The directory containing the PNG file. Must be the only file in
  43       the directory.
  44     png_filename: The full path to the PNG file to optimize.
  45
  46   Returns:
  47     The raw bytes of a PNG file, an optimized version of the input.
  48   """
  49   logging.debug('Crushing PNG image...')
  50   args = [OPTIMIZE_PNG_FILES]
  51   if optimization_level is not None:
  52     args.append('-o%d' % optimization_level)
  53   args.append(temp_dir)
  54   result = subprocess.call(args, stdout=sys.stderr)
  55   if result != 0:
  56     logging.warning('Warning: optimize-png-files failed (%d)', result)
  57   else:
  58     logging.debug('optimize-png-files succeeded')
  59
  60   with open(png_filename, 'rb') as png_file:
  61     return png_file.read()
  62
  63 def OptimizePng(png_data, optimization_level=None):
  64   """Optimize a PNG.
  65
  66   Args:
  67     png_data: The raw bytes of a PNG file.
  68
  69   Returns:
  70     The raw bytes of a PNG file, an optimized version of the input.
  71   """
  72   temp_dir = tempfile.mkdtemp()
  73   try:
  74     logging.debug('temp_dir = %s', temp_dir)
  75     png_filename = os.path.join(temp_dir, 'image.png')
  76     with open(png_filename, 'wb') as png_file:
  77       png_file.write(png_data)
  78     return OptimizePngFile(temp_dir, png_filename,
  79                            optimization_level=optimization_level)
  80
  81   finally:
  82     if os.path.exists(png_filename):
  83       os.unlink(png_filename)
  84     os.rmdir(temp_dir)
  85
  86 def OptimizeIcoFile(infile, outfile, optimization_level=None):
  87   """Read an ICO file, optimize its PNGs, and write the output to outfile.
  88
  89   Args:
  90     infile: The file to read from. Must be a seekable file-like object
  91       containing a Microsoft ICO file.
  92     outfile: The file to write to.
  93   """
  94   filename = os.path.basename(infile.name)
  95   icondir = infile.read(6)
  96   zero, image_type, num_images = struct.unpack('<HHH', icondir)
  97   if zero != 0:
  98     raise InvalidFile('First word must be 0.')
  99   if image_type not in (1, 2):
 100     raise InvalidFile('Image type must be 1 or 2.')
 101
 102   # Read and unpack each ICONDIRENTRY.
 103   icon_dir_entries = []
 104   for i in range(num_images):
 105     icondirentry = infile.read(16)
 106     icon_dir_entries.append(struct.unpack('<BBBBHHLL', icondirentry))
 107
 108   # Read each icon's bitmap data, crush PNGs, and update icon dir entries.
 109   current_offset = infile.tell()
 110   icon_bitmap_data = []
 111   for i in range(num_images):
 112     width, height, num_colors, r1, r2, r3, size, _ = icon_dir_entries[i]
 113     width = width or 256
 114     height = height or 256
 115     offset = current_offset
 116     icon_data = infile.read(size)
 117     if len(icon_data) != size:
 118       raise EOFError()
 119
 120     entry_is_png = IsPng(icon_data)
 121     logging.info('%s entry #%d: %dx%d, %d bytes (%s)', filename, i + 1, width,
 122                  height, size, 'PNG' if entry_is_png else 'BMP')
 123
 124     if entry_is_png:
 125       icon_data = OptimizePng(icon_data, optimization_level=optimization_level)
 126     elif width >= 256 or height >= 256:
 127       # TODO(mgiuca): Automatically convert large BMP images to PNGs.
 128       logging.warning('Entry #%d is a large image in uncompressed BMP format. '
 129                       'Please manually convert to PNG format before running '
 130                       'this utility.', i + 1)
 131
 132     new_size = len(icon_data)
 133     current_offset += new_size
 134     icon_dir_entries[i] = (width % 256, height % 256, num_colors, r1, r2, r3,
 135                            new_size, offset)
 136     icon_bitmap_data.append(icon_data)
 137
 138   # Write the data back to outfile.
 139   outfile.write(icondir)
 140   for icon_dir_entry in icon_dir_entries:
 141     outfile.write(struct.pack('<BBBBHHLL', *icon_dir_entry))
 142   for icon_bitmap in icon_bitmap_data:
 143     outfile.write(icon_bitmap)
 144
 145 def main(args=None):
 146   if args is None:
 147     args = sys.argv[1:]
 148
 149   parser = argparse.ArgumentParser(description='Crush Windows ICO files.')
 150   parser.add_argument('files', metavar='ICO', type=argparse.FileType('r+b'),
 151                       nargs='+', help='.ico files to be crushed')
 152   parser.add_argument('-o', dest='optimization_level', metavar='OPT', type=int,
 153                       help='optimization level')
 154   parser.add_argument('-d', '--debug', dest='debug', action='store_true',
 155                       help='enable debug logging')
 156
 157   args = parser.parse_args()
 158
 159   if args.debug:
 160     logging.getLogger().setLevel(logging.DEBUG)
 161
 162   for file in args.files:
 163     buf = StringIO.StringIO()
 164     file.seek(0, os.SEEK_END)
 165     old_length = file.tell()
 166     file.seek(0, os.SEEK_SET)
 167     OptimizeIcoFile(file, buf, args.optimization_level)
 168
 169     new_length = len(buf.getvalue())
 170     if new_length >= old_length:
 171       logging.info('%s : Could not reduce file size.', file.name)
 172     else:
 173       file.truncate(new_length)
 174       file.seek(0)
 175       file.write(buf.getvalue())
 176
 177       saving = old_length - new_length
 178       saving_percent = float(saving) / old_length
 179       logging.info('%s : %d => %d (%d bytes : %d %%)', file.name, old_length,
 180                    new_length, saving, int(saving_percent * 100))
 181
 182 if __name__ == '__main__':
 183   sys.exit(main())