Recently I found another interesting service: DURIS (Data URI Sprites). This is an automated solution for building Data:URI CSS Sprites for background images.

Basically you provide a page URL, then the service loads all styles of the page (both internal and external), finds all background images and encodes them into base64 (for data:URI format). As output, it provides a tar.gz file with HTML file and CSS files with encoded images in textual format.

The HTML contains the original pages with built-in code that checks browser version and plugs the styles with encoded images. There are several version of the styles for different browsers:

• MHTML – for IE version < 8 (only IE8 supports data:URI )
• data:URI – for all the other browsers
• original styles – for the case when Javascript is disabled and for IE7 under Vista (there is a bug related to security issue with cached MHTML background images)

The advantages are:

• all background images will be loaded in one HTTP request
• it’s possible to quickly rebuild CSS sprites after making changes

This is a new tool that’s in beta stage so I would not use it in production.
The tool written in Java and the authors are going to opensource it as soon as release-candidate is ready.
(via Habr article in Russian)

I remind that besides Data:URI Sprites we have classic Image Sprites that involve joining images into another big image (opposite to base64 supposed by Data:URI). There are number of tools exist for Image Sprites and most advanced that I know is SmartSprites.

The advantage of Image Sprites over Data:URI Sprites is that it’s supported by almost all browsers including very old versions. The disadvantage is that Image Sprites composition cannot be fully automated and every time should be controlled by web developer.