diff --git a/lib/compass/sass_extensions/functions/sprites.rb b/lib/compass/sass_extensions/functions/sprites.rb
index c676ba11..8b6ae8e9 100644
--- a/lib/compass/sass_extensions/functions/sprites.rb
+++ b/lib/compass/sass_extensions/functions/sprites.rb
@@ -1,20 +1,37 @@
+require 'chunky_png'
+
 module Compass::SassExtensions::Functions::Sprites
   def sprite_image(uri)
     uri = uri.value
     path, name = Compass::Sprites.path_and_name(uri)
-    y = 0
     last_spacing = 0
     default_spacing = number_from_var("#{name}-spacing")
+    width = 0
+    height = 0
     images = Compass::Sprites.sprites(name)
+    
+    # Calculation
     images.each do |image|
       current_spacing = number_from_var("#{name}-#{image[:name]}-spacing")
-      if y > 0
-        y += [current_spacing, last_spacing, default_spacing].max
+      if height > 0
+        height += [current_spacing, last_spacing, default_spacing].max
       end
-      image[:y] = y
-      y += image[:height]
+      image[:y] = height
+      height += image[:height]
       last_spacing = current_spacing
+      width = image[:width] if image[:width] > width
     end
+    
+    # Generation
+    output_png = ChunkyPNG::Image.new(width, height, ChunkyPNG::Color::TRANSPARENT)
+    images.each do |image|
+      input_png  = ChunkyPNG::Image.from_file(image[:file])
+      x = 0
+      y = image[:y]
+      output_png.replace input_png, x, y
+    end
+    output_png.save File.join(File.join(Compass.configuration.images_path, "#{path}.png"))
+    
     image_url(Sass::Script::String.new("#{path}.png"))
   end
 
diff --git a/lib/compass/sprites.rb b/lib/compass/sprites.rb
index 6130c84e..09ee3c2f 100644
--- a/lib/compass/sprites.rb
+++ b/lib/compass/sprites.rb
@@ -33,7 +33,7 @@ module Compass
           width, height = Compass::SassExtensions::Functions::ImageSize::ImageProperties.new(file).size
           images << {
             :name => File.basename(file, '.png'),
-            :filename => File.basename(file),
+            :file => file,
             :height => height,
             :width => width
           }
diff --git a/spec/sprites_spec.rb b/spec/sprites_spec.rb
index dbc2df2e..df83aeea 100644
--- a/spec/sprites_spec.rb
+++ b/spec/sprites_spec.rb
@@ -4,11 +4,22 @@ require "compass/sprites"
 describe Compass::Sprites do
   
   before :each do
-    Compass.configuration.images_path = File.dirname(__FILE__) + "/test_project/public/images"
+    @images_src_path = File.join(File.dirname(__FILE__), 'test_project', 'public', 'images')
+    @images_tmp_path = File.join(File.dirname(__FILE__), 'test_project', 'public', 'images-tmp')
+    FileUtils.cp_r @images_src_path, @images_tmp_path
+    Compass.configuration.images_path = @images_tmp_path
     Compass.configure_sass_plugin!
     Compass::Sprites.reset
   end
 
+  after :each do
+    FileUtils.rm_r @images_tmp_path
+  end
+
+  def image_size(file)
+    IO.read(File.join(@images_tmp_path, file))[0x10..0x18].unpack('NN')
+  end
+  
   def render(scss)
     scss = %Q(@import "compass"; #{scss})
     options = Compass.sass_engine_options
@@ -41,6 +52,7 @@ describe Compass::Sprites do
         background-position: 0 -10px;
       }
     CSS
+    image_size('squares.png').should == [20, 30]
   end
 
   it "should generate sprite classes with dimensions" do
@@ -66,6 +78,7 @@ describe Compass::Sprites do
         width: 20px;
       }
     CSS
+    image_size('squares.png').should == [20, 30]
   end
   
   it "should provide sprite mixin" do
@@ -95,6 +108,7 @@ describe Compass::Sprites do
         width: 20px;
       }
     CSS
+    image_size('squares.png').should == [20, 30]
   end
   
   # CUSTOMIZATIONS:
@@ -109,6 +123,7 @@ describe Compass::Sprites do
         background: url('/squares.png') no-repeat;
       }
     CSS
+    image_size('squares.png').should == [20, 30]
   end
 
   it "should calculate the spacing between images but not before first image" do
@@ -130,6 +145,7 @@ describe Compass::Sprites do
         background-position: 0 -43px;
       }
     CSS
+    image_size('squares.png').should == [20, 63]
   end
 
   it "should calculate the spacing between images" do
@@ -151,6 +167,7 @@ describe Compass::Sprites do
         background-position: 0 -43px;
       }
     CSS
+    image_size('squares.png').should == [20, 63]
   end
 
   it "should calculate the maximum spacing between images" do
@@ -173,6 +190,7 @@ describe Compass::Sprites do
         background-position: 0 -54px;
       }
     CSS
+    image_size('squares.png').should == [20, 74]
   end
 
   it "should calculate the maximum spacing between images in reversed order" do
@@ -195,6 +213,7 @@ describe Compass::Sprites do
         background-position: 0 -54px;
       }
     CSS
+    image_size('squares.png').should == [20, 74]
   end
 
   it "should calculate the default spacing between images" do
@@ -216,6 +235,7 @@ describe Compass::Sprites do
         background-position: 0 -32px;
       }
     CSS
+    image_size('squares.png').should == [20, 52]
   end
   
 end
\ No newline at end of file