Detect and conserve identical images in nymph.

r2/r2/lib/nymph.py

@@ -22,6 +22,7 @@
 
 import os
 import re
+import hashlib
 import Image
 import subprocess
 
@@ -44,10 +45,10 @@ def _extract_css_info(match):
 
 
 class SpritableImage(object):
-    def __init__(self, base_dir, filename, should_stretch=False):
-        self.filename = filename
+    def __init__(self, image, should_stretch=False):
+        self.image = image
         self.stretch = should_stretch
-        self.image = Image.open(os.path.join(base_dir, filename))
+        self.filenames = []
 
     @property
     def width(self):
@@ -89,12 +90,17 @@ def _load_spritable_images(css_filename):
                 continue
 
             image_filename, should_stretch = _extract_css_info(m)
+            image = Image.open(os.path.join(css_location, image_filename))
+            image_hash = hashlib.md5(image.convert("RGBA").tostring()).hexdigest()
 
-            if image_filename not in images:
-                images[image_filename] = SpritableImage(css_location, image_filename, should_stretch)
+            if image_hash not in images:
+                images[image_hash] = SpritableImage(image, should_stretch)
             else:
-                assert images[image_filename].stretch == should_stretch
-    return images.values()
+                assert images[image_hash].stretch == should_stretch
+            images[image_hash].filenames.append(image_filename)
+
+    # Sort images by filename to group the layout by names when possible.
+    return sorted(images.values(), key=lambda i: i.filenames[0])
 
 
 def _generate_sprite(images, sprite_path):
@@ -149,7 +155,8 @@ def _rewrite_css(css_filename, sprite_path, images):
     # map filenames to coordinates
     locations = {}
     for image in images:
-        locations[image.filename] = image.sprite_location
+        for filename in image.filenames:
+            locations[filename] = image.sprite_location
 
     def rewrite_sprite_reference(match):
         image_filename, should_stretch = _extract_css_info(match)