Last year, Google announced WebP, a new image compression format meant to reduce the size of JPEG images. WebP is based on a algorithm borrowed from the VP8 codec used by WebM to encode and compress video. After compressing 1M images, Google concluded at that time that WebP shrinks the image size by an average of 39%, making it attractive as a new image format considering it is open source and 65% of total bytes sent over the Internet represent images.
The new format has found support in Chrome 9+ and Opera 11.10+ (Opera Turbo). Opera made several improvements to speed up page downloads, the “most noticeable difference is probably WebP”. As a result, they claim a 22% less data transferred and a 260% speed improvement.
Mozilla, one of the main open source supporters, did not accept the format, Jeff Muizelaar complaining among others that the Google’s study on WebP’s performance “has some problems and as a result, isn't very convincing.” He also remarked WebP’s lack of some features such as color representation “other than 4:2:0 YCrCb”, “EXIF data and ICC color profiles”, and alpha channel support, which is also not supported by JPEG. Muizelaar also mentioned that it is unlikely that major websites serving images to compress them using WebP, considering that “Flickr compresses their images at libjpeg quality of 96 and Facebook at 85”, and are not striving to get smaller image sizes. Also, Microsoft is quite unlikely to support WebP since they have proposed JPEG XR.
A Mozilla enhancement request, “Implement WebP image support”, was closed with the resolution “Won’t Fix”. Robert O'Callahan from Mozilla commented on the request a month ago: “We don't want to implement what WebP is today,” leaving room for that if Google would improve it in the future: “If it's much better tomorrow, file a new bug or possibly reopen this one.”
But Google announced last week that they have enhanced WebP, publishing a new study:
- higher image quality (samples)
- progressive decoding to be able to decode an image as soon as download begins
- a fancy upsampler which reduces the pixelation of strong edges
- parameterized Spatial Noise Shaping
- JNI support
Google also mentioned they work on adding alpha channel support, more speed improvements and a complete metadata specification.
Among adopters, Google mentioned GMail, Picasa, Google Instant Previews, and a number of applications or plugins for major image editing/rendering applications such as Photoshop, Microsoft Office 2010, Windows Media Center and Photo Edit, plus codec ports to Max OS and Linux, in an attempt to push the adoption of the new image format. Although, the new codec and the JPEG-WebP comparison study responds to most of Mozilla’s critique, there is no word from them so far whether they will include it in Firefox or not. For some reasons, they seem reluctant to do so while the community presses hard for its adoption, if the comments on the Firefox enhancement request and Muizelaar’s blog post are of any relevance. Only time will tell if WebP will be largely adopted or it will remain limited to Google and Opera.