Google's WebP crosshairs target PNG, not just JPEG

Google's image format started as a rival to JPEG, but new features mean it could take on Portable Network Graphics, too.

Google launched WebP to outdo JPEG. Now a new version is designed to take on another dominant graphics format on the Web, PNG.

WebP is based on the open-source compression technology used in Google's WebM video encoding technology, and with it, Google hopes to reduce Web page file sizes and thereby speed up the Net. There are plenty of challenges for the technology, but Google just made WebP a bit more competitive through the addition of two major features.

First is a "lossless" compression option that can image data without loss of fidelity. Second is support for an "alpha channel," which lets designers designate part of an image as transparent.

That's useful for video game graphics, icons in user interfaces, and other objects that aren't simple shapes placed in front of a background. Designers today often must choose between JPEG, which doesn't support alpha channels, and PNG (Portable Network Graphics), which does, but which in many cases doesn't compress images as well as JPEG.

"Photographic images typically encoded as JPEG can be encoded in WebP lossy mode to achieve smaller file size. Icons and graphics can be encoded better in WebP lossless mode than in PNG. WebP lossy with alpha can be used to create transparent images that have minimal visual degradation, yet are much smaller in file size," Google programmers Jyrki Alakuijala, Vikas Arora, and Urvang Joshi said in a blog post last week.

And WebP could appeal to a peculiar niche on the Net: the animated GIF crowd, who help keep the gradually fading Graphics Interchange Format alive because it can be turned into a crude multi-frame video. Animated WebP support, though, remains a work in progress.

But getting a new image format to catch on is tough. Microsoft has tried for years with a format first called Windows Media Photo and now standardized as JPEG XR. It also offers better compression than JPEG, alpha-channel support, and a lossless mode, but it's a rarity in the real world.

One area where JPEG XR found a foothold is the Flash Player 11.

Curiously, Mozilla has begun kicking the JPEG XR tires, contemplating the possibility of supporting it in Firefox.

Programmers who use the WebGL--a 3D graphics technology for the Web--apparently also would like a combination of compression and alpha-channel support.

Google is eager to spread WebP far and wide. Mozilla is more cautious, though, given the concern that "every image format that becomes 'part of the Web platform' exacts a cost for all time."

WebP's prospects also could be impaired by the fact that it isn't a standard. A standard is a safer bet for camera makers and others considering the prospect of supporting a new file format.

Still, Google's control over WebM video hasn't stopped it from being included in Firefox and Opera browsers. And Google continues to improve WebP and WebM with faster encoding and decoding as well as better image quality.