ImageBundle

ImageBundleHelper adds view helper image_bundle. A helper which bundles individual local images into a single CSS sprite thereby reducing the number of HTTP requests needed to render the page.

Yahoo's Exceptional Performance team found that the number of HTTP requests has the biggest impact on page rendering speed. You can inspect your site's performance with the excellent Firefox add-on YSlow.

Usage

Use ImageBundle to automatically replace individual local images into CSS sprites.

Demo

A demo of ImageBundle is available at http://thecodemill.biz/image_bundle/.

Note on image_tag helper

Rails' image_tag helper adds a query parameter to the image URL to 'bust caches'. It ads either the RAILS_ASSET_ID environment variable or the image's modification time. This is the wrong thing to do. Caches should be managed through the use of HTTP headers such as Cache-Control, Last-Modified, Expires and of course the HTTP response code. Adding the modification time is the same as using as using ETags in apache or IIS, see http://developer.yahoo.com/performance/rules.html#etags for an explanation why it is better to avoid using ETags in favor of proper Expires headers.

This plugin doesn't accept image URLS that include query parameters as they are either dynamically generated and shouldn't be part of a sprite or they promote a bad practice.

If you like to use the image_tag helper I recommend you a) configure the webserver of you static content to return proper headers and b) to overwrite ActionView::Helpers::AssetTagsHelper#rewrite_asset_path! like so:

module ActionView module Helpers module AssetTagHelper def rewrite_asset_path!(source) end end end end

Create a file lib/asset_tag_helper.rb and load it at the end of your config/environment.rb file like so:

require File.join(File.dirname(FILE), '../lib/asset_tag_helper')

License & Author

Copyright (C) 2007 Bart Teeuwisse

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA