cope with PNG 8 pallete with semi transparency (bug 621033)

apps/amo/tests/test_amo_utils.py

@@ -1,4 +1,8 @@
 # -*- coding: utf-8 -*-
+import os
+import tempfile
+
+from django.conf import settings
 from django.core.validators import ValidationError
 
 from nose.tools import eq_, assert_raises
@@ -44,3 +48,16 @@ def test_slugify():
 def test_resize_image():
     # src and dst shouldn't be the same.
     assert_raises(Exception, resize_image, 't', 't', 'z')
+
+
+def test_resize_transparency():
+    src = os.path.join(settings.ROOT, 'apps', 'amo', 'tests',
+                       'images', 'transparent.png')
+    dest = tempfile.mkstemp()[1]
+    expected = src.replace('.png', '-expected.png')
+    try:
+        resize_image(src, dest, (32, 32), remove_src=False)
+        assert open(dest, 'rb').read() == open(expected, 'rb').read()
+    finally:
+        if os.path.exists(dest):
+            os.remove(dest)

apps/amo/utils.py

@@ -19,7 +19,7 @@ from django.utils.encoding import smart_str, smart_unicode
 
 from easy_thumbnails import processors
 import pytz
-from PIL import Image
+from PIL import Image, ImageFile, PngImagePlugin
 
 from . import logger_log as log
 from translations.models import Translation
@@ -241,18 +241,55 @@ def clear_messages(request):
     """
     Clear any messages out of the messages framework for the authenticated
     user.
-    Docs:
-    http://docs.djangoproject.com/en/dev/ref/contrib/messages/#expiration-of-messages
+    Docs: http://bit.ly/dEhegk
     """
     for message in messages.get_messages(request):
         pass
 
 
+# From: http://bit.ly/eTqloE
+# Without this, you'll notice a slight grey line on the edges of
+# the adblock plus icon.
+def patched_chunk_tRNS(self, pos, len):
+    i16 = PngImagePlugin.i16
+    s = ImageFile._safe_read(self.fp, len)
+    if self.im_mode == "P":
+        self.im_info["transparency"] = map(ord, s)
+    elif self.im_mode == "L":
+        self.im_info["transparency"] = i16(s)
+    elif self.im_mode == "RGB":
+        self.im_info["transparency"] = i16(s), i16(s[2:]), i16(s[4:])
+    return s
+PngImagePlugin.PngStream.chunk_tRNS = patched_chunk_tRNS
+
+
+def patched_load(self):
+    if self.im and self.palette and self.palette.dirty:
+        apply(self.im.putpalette, self.palette.getdata())
+        self.palette.dirty = 0
+        self.palette.rawmode = None
+        try:
+            trans = self.info["transparency"]
+        except KeyError:
+            self.palette.mode = "RGB"
+        else:
+            try:
+                for i, a in enumerate(trans):
+                    self.im.putpalettealpha(i, a)
+            except TypeError:
+                self.im.putpalettealpha(trans, 0)
+            self.palette.mode = "RGBA"
+    if self.im:
+        return self.im.pixel_access(self.readonly)
+Image.Image.load = patched_load
+
+
 def resize_image(src, dst, size, remove_src=True):
     """Resizes and image from src, to dst."""
     if src == dst:
         raise Exception("src and dst can't be the same: %s" % src)
     im = Image.open(src)
+    im = im.convert('RGBA')
     im = processors.scale_and_crop(im, size)
     im.save(dst, 'png')