Issue 2038 - Convert palette images with transparency to RGBA before pasting

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
 
 try:
@@ skipping 39 matching lines @@
     im2 if im2.mode == mode else im2.convert(mode),
   )
 
 def filter_contrastToAlpha(image, baseDir):
   # In order to generate an alpha channel for images using a palette, we must
   # 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 case the transparency is
-  # specified in bytes (pngout loves to that shit), we can't associate that

[Wladimir Palant, 2015/02/24 17:08:13]

Want to censor out the remark in parentheses?

[Sebastian Noack, 2015/02/24 17:19:23]

Done.

-  # value with transparent pixels. Moreover, some versions of PIL raise a
-  # warning when such images are pasted into another image.
+  # specified in bytes (pngout loves to do that), we can't associate that value
+  # with transparent pixels. Moreover, some versions of PIL raise a warning
+  # when such images are pasted into another image.
   if image.mode == 'P' and 'transparency' in image.info:
-    image = image.convert("RGBA")

[Wladimir Palant, 2015/02/24 17:08:13]

Nit: I don't mind which quotation marks you use but please be consistent :)

[Sebastian Noack, 2015/02/24 17:19:23]

Done.

+    image = image.convert('RGBA')
 
-  # Image.paste() isgnores the alpha channel of the pasted image, but expects

[Wladimir Palant, 2015/02/24 17:08:13]

isgnores => ignores

[Sebastian Noack, 2015/02/24 17:19:23]

This has already been fixed by the previous changeset.

-  # the mask to be passed as sperate argument. So we have to extract the alpha

[Wladimir Palant, 2015/02/24 17:08:13]

sperate => separate

[Sebastian Noack, 2015/02/24 17:19:23]

Done.

+  # Image.paste() ignores the alpha channel of the pasted image, but expects
+  # the mask to be passed as separate argument. So we have to extract the alpha
   # channel (if any) from the image we are going to paste.
   if image.mode in ('RGBA', 'LA'):
     mask = image.split()[image.getbands().index('A')]
   else:
     mask = None
 
   alpha = Image.new('L', image.size, 255)
   alpha.paste(image, mask=mask)
   alpha = ImageOps.invert(alpha)
   alpha = ImageOps.autocontrast(alpha)
@@ skipping 22 matching lines @@
     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)
 
     file = image_to_file(image, filename)
     try:
       files[filename] = file.read()
     finally:
       file.close()