Google Introduces WebP Image Format

Google has introduced the new WebP image format as another in a series of moves the company has made to speed up the Web.

Google has introduced a new Web image format, known as WebP, with the goal of speeding up the performance of Websites.

In a Sept. 30 blog post, Richard Rabbat, a Google product manager, said Google has released a developer preview of the WebP technology "that promises to significantly reduce the byte size of photos on the Web, allowing Websites to load faster than before."

Rabbat said images and photos make up about 65 percent of the bytes transmitted per Web page today. "They can significantly slow down a user's Web experience, especially on bandwidth-constrained networks such as a mobile network," he said. "Images on the Web consist primarily of lossy formats such as JPEG, and to a lesser extent lossless formats such as PNG and GIF. Our team focused on improving compression of the lossy images, which constitute the larger percentage of images on the Web today."

Google used an image compressor based on its VP8 codec to beat the performance that JPEG delivers. The company open-sourced the VP8 codec at its Google I/O developer conference in May 2010.

"We applied the techniques from VP8 video intra frame coding to push the envelope in still image coding," Rabbat said." We also adapted a very lightweight container based on RIFF. While this container format contributes a minimal overhead of only 20 bytes per image, it is extensible to allow authors to save meta-data they would like to store."
To test the effects of WebP, Rabbat said Google "we randomly picked about 1,000,000 images from the Web (mostly JPEGs and some PNGs and GIFs) and re-encoded them to WebP without perceptibly compromising visual quality. This resulted in an average 39 percent reduction in file size. We expect that developers will achieve in practice even better file size reduction with WebP when starting from an uncompressed image."

Also, Google has created a site for developers to assess the performance of WebP versus other formats. The company also will release a conversion tool to convert images to the WebP format. And Rabbat said Google hopes to work with the browser and Web developer community to beef up the WebP spec and to add native support for WebP.

Indeed, "we are developing a patch for WebKit to provide native support for WebP in an upcoming release of Google Chrome," he said.

Moreover, Rabbat said WebP is another in a series of moves Google has recently made to help speed up the Web, including the Page Speed Firefox extension, the Speed Tracer Chrome extension, and a set of closure tools to developers help build rich Web applications with optimized JavaScript code.