Google has announced that Gmail and Picasa as well as its Chrome browser are now using WebP, the image compression format it open sourced last fall in an effort to replace the aging JPEG standard.
With a Friday blog post, the company also said that it has made several improvements to the technology since it was first unveiled.
When Google open sourced WebP last September, it claimed the new image format would reduce the size of web images by a good 40 per cent. The format is based on VP8, the video codec Google acquired with its purchase of On2 Technologies early last year and promptly open sourced as part of the new media format known as WebM.
Like JPEG, WebP uses "lossy" compression, discarding small pieces of an image as it works to make the file smaller. Google has essentially taken the techniques used with VP8 video intra-frame coding and applied them to image coding. WebP uses predictive coding, predicting the values in a block of pixels using the values in neighboring blocks and encoding only the difference between the actual value and the prediction. This difference is known as the residual, which typically contains many zeros that can be compressed more effectively.
Since the release the format, Google has added a fancy unsampler – designed to reduce pixelation around image edges – and WebP data can now be decoded as it is being downloaded from the web. This means portions of an image can be displayed before the entire file has been downloaded.
The company has also improved compression by working to divide images into sections that exhibit "similar compressibility". "For each of these segments, we tune the amount of compression and filtering differently, and bits are redistributed where they are most useful," Google said.
WebP is supported not only by Google Chrome but also Opera's desktop browser. Separately, Opera is using the format to improve Opera Turbo, its service for compressing entire webpages for mobile phones and other machines burdened by low-bandwidth net connections. You can also share WebP images via Gmail and Google's dedicated photo sharing app, Picasa, and the company will soon bring WebP support to App Engine, its so-called development cloud for building and hosting applications on its famously distributed infrastructure.
Google also points to several tools that let you manipulate WebP on your own, including Pixelmator, ImageMagick, the WebP plugin for Photoshop, and the Java VP8 decoder. You can also download the WebP codec onto Windows machines to add support for Microsoft Office and Windows Media, and you can also find support for Mac OS X, Debian, OpenSUSE, Gentoo, and the Apache HTTP Server.
Mozilla, Apple, and Microsoft have yet to adopt the format in their browsers. ®