[story via InformationWeek]

Continuing its campaign to speed up the Web, Google on Thursday released a developer preview of a new open-source image format called WebP that reduces image file sizes by an average of a third more than what JPEG compression can accomplish.

Speed for Google is critical to making Web applications and mobile applications competitive with desktop applications and to a positive user experience in general. Smaller images mean that Web sites load faster.

Google says that images are the single largest factor in Web page latency, representing 65% of the bytes transmitted when a Web page request is made. So its engineers have tried to make images smaller by improving lossy image compression techniques, which tend to produce smaller image files than lossless image compression schemes.

The JPEG format is the dominant lossy image file type on the Web. WebP, developed using compression technology from the VP8 video codec that Google acquired from On2 and open-sourced in May, compresses image files 39% smaller on average than JPEG, based on a random sample of one million images selected from the Web.

As a developer release, Google is providing a lightweight decoder for WebP files (libvpx) and a command line tool (webpconv) for converting images to the WebP format and back. Consumers won’t really get a look at WebP images until Google’s engineers finish implementing WebP in the company’s Chrome Web browser.

But the company has created a preview gallery for those who wish to do a side-by side comparison. Because WebP is not yet supported in any browser, Google has wrapped the WebP images in a PNG frame so they can be displayed.

It remains to be seen whether WebP will be drawn into a patent battle. In theory, WebP, as an open-source format, should be preferable to JPEG, which while beyond its 20-year patent term has been the target of patent claims, however weak, in the past. Given that an April e-mail attributed to Apple CEO Steve Jobs states, “A patent pool is being assembled to go after Theora and other ‘open source’ codecs now,” a legal assault on the VP8 codec, perhaps affecting WebP, seems possible.