FIX: use correct command line attribute for `gifsicle` while scale down the gif.

app/models/optimized_image.rb

@@ -236,11 +236,12 @@ class OptimizedImage < ActiveRecord::Base
 
   def self.resize_instructions_animated(from, to, dimensions, opts = {})
     ensure_safe_paths!(from, to)
+    resize_method = opts[:scale_image] ? "scale" : "resize-fit"
 
     %W{
       gifsicle
       --colors=#{opts[:colors] || 256}
-      --resize-fit #{dimensions}
+      --#{resize_method} #{dimensions}
       --optimize=3
       --output #{to}
       #{from}

lib/upload_creator.rb

@@ -245,14 +245,16 @@ class UploadCreator
 
       from = @file.path
       to = down_tempfile.path
+      scale = (from =~ /\.GIF$/i) ? "0.5" : "50%"
 
       OptimizedImage.ensure_safe_paths!(from, to)
 
       OptimizedImage.downsize(
         from,
         to,
-        "50%",
+        scale,
         allow_animation: allow_animation,
+        scale_image: true,
         raise_on_error: true
       )