detect animated images (bug 550641)

apps/amo/tests/test_helpers.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 from datetime import datetime
+import os
 
 from django.conf import settings
 from django.core import mail
@@ -14,6 +15,7 @@ import test_utils
 
 import amo
 from amo import urlresolvers, utils, helpers
+from amo.utils import is_animated_image
 from versions.models import License
 
 
@@ -269,3 +271,17 @@ class AbuseDisabledBase:
 
         res = self.client.post(self.full_page)
         eq_(res.status_code, 404)
+
+
+def get_image_path(name):
+    return os.path.join(settings.ROOT, 'apps', 'amo', 'tests', 'images', name)
+
+
+class TestAnimatedImages(test_utils.TestCase):
+
+    def test_animated_images(self):
+        assert is_animated_image(open(get_image_path('animated.png')))
+        assert not is_animated_image(open(get_image_path('non-animated.png')))
+
+        assert is_animated_image(open(get_image_path('animated.gif')))
+        assert not is_animated_image(open(get_image_path('non-animated.gif')))

apps/amo/utils.py

@@ -254,6 +254,30 @@ def resize_image(src, dst, size):
     os.remove(src)
 
 
+def is_animated_image(photo, size=100000):
+    img = Image.open(photo)
+    if img.format == 'PNG':
+        photo.seek(0)
+        data = ''
+        while True:
+            chunk = photo.read(size)
+            if not chunk:
+                break
+            data += chunk
+            acTL, IDAT = data.find('acTL'), data.find('IDAT')
+            if acTL > -1 and acTL < IDAT:
+                return True
+        return False
+    elif img.format == 'GIF':
+        # See the PIL docs for how this works:
+        # http://www.pythonware.com/library/pil/handbook/introduction.htm
+        try:
+            img.seek(1)
+        except EOFError:
+            return False
+        return True
+
+
 class MenuItem():
     """Refinement item with nestable children for use in menus."""
     url, text, selected, children = ('', '', False, [])