Issue 1897 - Compress auto-generated images with pngout

imageConversion.py

 # coding: utf-8
 
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import os
 import re
-from StringIO import StringIO
 
 try:
   from PIL import Image
   from PIL import ImageOps
 except ImportError:
   import Image
   import ImageOps
 
+from imageCompression import image_to_file
+
 def get_alpha(image):
   if image.mode in ('RGBA', 'LA'):
     return image.split()[image.getbands().index('A')]
 
   # In order to generate an alpha channel for images using a palette, we
   # convert the image to RGBA. It's important to use RGBA, not LA (grayscale+alpha),
   # since PIL can't reliably convert P to LA. Also initially, we created an
   # alpha channel by replacing opaque pixels with a high mark and transparent
   # pixels with a low mark. However, it turned out that you can't rely on the
   # value of Image.info['transparency'] since in some cases it might be an
@@ skipping 60 matching lines @@
   for filename, chain in metadata.items('convert_img'):
     baseDir = os.path.dirname(metadata.option_source('convert_img', filename))
     steps = re.split(r'\s*->\s*', chain)
     image = load_image(os.path.join(baseDir, *steps.pop(0).split('/')))
 
     for step in steps:
       filter, args = re.match(r'([^(]+)(?:\((.*)\))?', step).groups()
       args = re.split(r'\s*,\s*', args) if args else ()
       image = globals()['filter_' + filter](image, baseDir, *args)
 
-    f = StringIO()
-    f.name = filename
-    image.save(f)
-    files[filename] = f.getvalue()
+    file = image_to_file(image, filename)
+    try:
+      files[filename] = file.read()
+    finally:
+      file.close()