FEATURE: allow animated thumbnails

app/models/optimized_image.rb

@@ -79,19 +79,30 @@ class OptimizedImage < ActiveRecord::Base
   end
 
   def self.resize(from, to, width, height, allow_animation=false)
-    from << "[0]" unless allow_animation
     # NOTE: ORDER is important!
-    instructions = %W{
-      #{from}
-      -background transparent
-      -gravity center
-      -thumbnail #{width}x#{height}^
-      -extent #{width}x#{height}
-      -interpolate bicubic
-      -unsharp 2x0.5+0.7+0
-      -quality 98
-      #{to}
-    }.join(" ")
+    instructions = if allow_animation
+      %W{
+        #{from}
+        -coalesce
+        -gravity center
+        -thumbnail #{width}x#{height}^
+        -extent #{width}x#{height}
+        -layers optimize
+        #{to}
+      }.join(" ")
+    else
+      %W{
+        #{from}[0]
+        -background transparent
+        -gravity center
+        -thumbnail #{width}x#{height}^
+        -extent #{width}x#{height}
+        -interpolate bicubic
+        -unsharp 2x0.5+0.7+0
+        -quality 98
+        #{to}
+      }.join(" ")
+    end
 
     `convert #{instructions}`
 

app/models/upload.rb

@@ -26,7 +26,7 @@ class Upload < ActiveRecord::Base
 
   def create_thumbnail!(width, height)
     return unless SiteSetting.create_thumbnails?
-    thumbnail = OptimizedImage.create_for(self, width, height)
+    thumbnail = OptimizedImage.create_for(self, width, height, allow_animation: SiteSetting.allow_animated_thumbnails)
     if thumbnail
       optimized_images << thumbnail
       self.width = width

config/locales/server.en.yml

@@ -975,6 +975,7 @@ en:
 
     allow_uploaded_avatars: "Allow users to upload custom avatars."
     allow_animated_avatars: "Allow users to use animated gif avatars. WARNING: run the avatars:refresh rake task after changing this setting."
+    allow_animated_thumbnails: "Generates animated thumbnails of animated gifs."
     automatically_download_gravatars: "Download Gravatars for users upon account creation or email change."
     digest_topics: "The maximum number of topics to display in the email digest."
     digest_min_excerpt_length: "Minimum post excerpt in the email digest, in characters."

config/site_settings.yml

@@ -478,6 +478,7 @@ files:
   allow_animated_avatars:
     client: true
     default: false
+  allow_animated_thumbnails: false
 
 trust:
   default_trust_level: