Add an option to ThumbnailProcessor to override animated thumbnail generation.

Closes #515

lib/paperclip/style.rb

@@ -72,7 +72,7 @@ module Paperclip
     # Supports getting and setting style properties with hash notation to ensure backwards-compatibility
     # eg. @attachment.styles[:large][:geometry]@ will still work
     def [](key)
-      if [:name, :convert_options, :whiny, :processors, :geometry, :format].include?(key)
+      if [:name, :convert_options, :whiny, :processors, :geometry, :format, :animated].include?(key)
         send(key)
       elsif defined? @other_args[key]
         @other_args[key]
@@ -80,7 +80,7 @@ module Paperclip
     end
 
     def []=(key, value)
-      if [:name, :convert_options, :whiny, :processors, :geometry, :format].include?(key)
+      if [:name, :convert_options, :whiny, :processors, :geometry, :format, :animated].include?(key)
         send("#{key}=".intern, value)
       else
         @other_args[key] = value

lib/paperclip/thumbnail.rb

@@ -2,7 +2,8 @@ module Paperclip
   # Handles thumbnailing images that are uploaded.
   class Thumbnail < Processor
 
-    attr_accessor :current_geometry, :target_geometry, :format, :whiny, :convert_options, :source_file_options
+    attr_accessor :current_geometry, :target_geometry, :format, :whiny, :convert_options,
+                  :source_file_options, :animated
 
     # List of formats that we need to preserve animation
     ANIMATED_FORMATS = %w(gif)
@@ -25,6 +26,7 @@ module Paperclip
       @convert_options     = options[:convert_options]
       @whiny               = options[:whiny].nil? ? true : options[:whiny]
       @format              = options[:format]
+      @animated            = options[:animated].nil? ? true : options[:animated]
 
       @source_file_options = @source_file_options.split(/\s+/) if @source_file_options.respond_to?(:split)
       @convert_options     = @convert_options.split(/\s+/)     if @convert_options.respond_to?(:split)
@@ -86,7 +88,7 @@ module Paperclip
 
     # Return true if the format is animated
     def animated?
-      ANIMATED_FORMATS.include?(@current_format[1..-1]) && (ANIMATED_FORMATS.include?(@format.to_s) || @format.blank?)
+      @animated && ANIMATED_FORMATS.include?(@current_format[1..-1]) && (ANIMATED_FORMATS.include?(@format.to_s) || @format.blank?)
     end
   end
 end

test/thumbnail_test.rb

@@ -310,5 +310,23 @@ class ThumbnailTest < Test::Unit::TestCase
         assert_equal @thumb.transformation_command.first, "-coalesce"
       end
     end
+
+    context "with animated option set to false" do
+      setup do
+       @thumb = Paperclip::Thumbnail.new(@file, :geometry => "50x50", :animated => false)
+      end
+
+      should "output the gif format" do
+        dst = @thumb.make
+        cmd = %Q[identify "#{dst.path}"]
+        assert_match /GIF/, `#{cmd}`.chomp
+      end
+
+      should "create the single frame thumbnail when sent #make" do
+        dst = @thumb.make
+        cmd = %Q[identify -format "%wx%h" "#{dst.path}"]
+        assert_equal "50x50", `#{cmd}`.chomp
+      end
+    end
   end
 end