Add animated image support in thumbnail generation

There's a case when you really don't want to make a thumbnail of only the first frame, such as making thumbnail for GIF image. This patch will check that the source and output format is an animated format, and not calling `[0]` on it.

Closes #454

lib/paperclip/thumbnail.rb

@@ -4,6 +4,9 @@ module Paperclip
 
     attr_accessor :current_geometry, :target_geometry, :format, :whiny, :convert_options, :source_file_options
 
+    # List of formats that we need to preserve animation
+    ANIMATED_FORMATS = %w(gif)
+
     # Creates a Thumbnail object set to work on the +file+ given. It
     # will attempt to transform the image into one defined by +target_geometry+
     # which is a "WxH"-style string. +format+ will be inferred from the +file+
@@ -58,7 +61,7 @@ module Paperclip
 
         parameters = parameters.flatten.compact.join(" ").strip.squeeze(" ")
 
-        success = Paperclip.run("convert", parameters, :source => "#{File.expand_path(src.path)}[0]", :dest => File.expand_path(dst.path))
+        success = Paperclip.run("convert", parameters, :source => "#{File.expand_path(src.path)}#{'[0]' unless animated?}", :dest => File.expand_path(dst.path))
       rescue Cocaine::ExitStatusError => e
         raise PaperclipError, "There was an error processing the thumbnail for #{@basename}" if @whiny
       rescue Cocaine::CommandNotFoundError => e
@@ -77,5 +80,12 @@ module Paperclip
       trans << "-crop" << %["#{crop}"] << "+repage" if crop
       trans
     end
+
+    protected
+
+    # Return true if the format is animated
+    def animated?
+      ANIMATED_FORMATS.include?(@current_format[1..-1]) && (ANIMATED_FORMATS.include?(@format.to_s) || @format.blank?)
+    end
   end
 end

test/thumbnail_test.rb

@@ -254,4 +254,53 @@ class ThumbnailTest < Test::Unit::TestCase
       end
     end
   end
+
+  context "An animated gif" do
+    setup do
+      @file = File.new(File.join(File.dirname(__FILE__), "fixtures", "animated.gif"), 'rb')
+    end
+
+    teardown { @file.close }
+
+    should "start with 12 frames with size 100x100" do
+      cmd = %Q[identify -format "%wx%h" "#{@file.path}"]
+      assert_equal "100x100"*12, `#{cmd}`.chomp
+    end
+
+    context "with static output" do
+      setup do
+       @thumb = Paperclip::Thumbnail.new(@file, :geometry => "50x50", :format => :jpg)
+      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
+
+    context "with animated output format" do
+      setup do
+       @thumb = Paperclip::Thumbnail.new(@file, :geometry => "50x50", :format => :gif)
+      end
+
+      should "create the 12 frames thumbnail when sent #make" do
+        dst = @thumb.make
+        cmd = %Q[identify -format "%wx%h" "#{dst.path}"]
+        assert_equal "50x50"*12, `#{cmd}`.chomp
+      end
+    end
+
+    context "with omitted output format" do
+      setup do
+       @thumb = Paperclip::Thumbnail.new(@file, :geometry => "50x50")
+      end
+
+      should "create the 12 frames thumbnail when sent #make" do
+        dst = @thumb.make
+        cmd = %Q[identify -format "%wx%h" "#{dst.path}"]
+        assert_equal "50x50"*12, `#{cmd}`.chomp
+      end
+    end
+  end
 end