Give thumbnails a checkerboard bg for transparent images

etiquette/helpers.py

@@ -2,6 +2,7 @@ import datetime
 import math
 import mimetypes
 import os
+import PIL.Image
 
 from . import constants
 from . import exceptions
@@ -68,6 +69,17 @@ def binding_filler(column_names, values, require_all=True):
     bindings = [values[column] for column in column_names]
     return (qmarks, bindings)
 
+def checkerboard_image(color_1, color_2, image_size, checker_size):
+    image = PIL.Image.new('RGB', image_size, color_1)
+    checker = PIL.Image.new('RGB', (checker_size, checker_size), color_2)
+    offset = True
+    for y in range(0, image_size[1], checker_size):
+        for x in range(0, image_size[0], checker_size * 2):
+            x += offset * checker_size
+            image.paste(checker, (x, y))
+        offset = not offset
+    return image
+
 def chunk_sequence(sequence, chunk_length, allow_incomplete=True):
     '''
     Given a sequence, divide it into sequences of length `chunk_length`.

etiquette/objects.py

@@ -506,7 +506,6 @@ class Photo(ObjectBase):
             self.photodb.log.debug('Thumbnailing %s' % self.real_filepath)
             try:
                 image = PIL.Image.open(self.real_filepath)
-                image = image.convert('RGB')
             except (OSError, ValueError):
                 pass
             else:
@@ -519,6 +518,20 @@ class Photo(ObjectBase):
                 )
                 if new_width < width:
                     image = image.resize((new_width, new_height))
+
+                if image.mode == 'RGBA':
+                    background = helpers.checkerboard_image(
+                        color_1=(256, 256, 256),
+                        color_2=(128, 128, 128),
+                        image_size=image.size,
+                        checker_size=8,
+                    )
+                    # Thanks Yuji Tomita
+                    # http://stackoverflow.com/a/9459208
+                    background.paste(image, mask=image.split()[3])
+                    image = background
+
+                image = image.convert('RGB')
                 image.save(hopeful_filepath, quality=50)
                 return_filepath = hopeful_filepath