WebP Poses Threat to GIF, JPEG, PNG

Stephen Yagielowicz

LOS ANGELES — Google has announced the addition of lossless compression and transparency encoding to its WebP image format, providing two more advantages over legacy Internet graphics formats.

According to Google, WebP is a new image format that provides both lossless and lossy compression, as well as a range of advanced features, for images used online.

“WebP lossless images are 28 percent smaller in size compared to PNGs,” claims the product’s website. “WebP lossy images are 25-34 percent smaller in size compared to JPEG images at equivalent SSIM index.”

Those are significant achievements, but only two of the benefits of the WebP format; which also supports losseless alpha channel transparency with the addition of 22 percent overhead in additional bytes. Google says the format also supports animation, ICC color profiling, XMP meta-data and tiling.

“Webmasters and web developers can use the WebP image format to create smaller and richer images that can help make the web faster,” the site adds, crediting the power of predictive coding with enabling WebP’s high quality image encoding — a similar process to that used by the VP8 video codec of sister project, WebM, for compressing keyframes.

“Predictive coding uses the values in neighboring blocks of pixels to predict the values in a block, and then encodes only the difference (residual) between the actual values and the prediction,” states a Google rep. “The residuals typically contain many zero values, which can be compressed much more effectively. The residuals are then transformed, quantized and entropy-coded as usual. WebP also uses variable block sizes.”

WebP is natively supported by Google Chrome and the Google Chrome Frame plugin for Internet Explorer, Opera 11.10 and the Android Ice Cream Sandwich mobile OS.

To get started, webmasters and designers can convert their JPEG and PNG images to the WebP format with the cwebp conversion tool for Linux, Windows and Mac OS X.

Check out the sample galleries for side-by-side image quality and file size comparisons.

While universal compatibility is some time away, graphics heavy content marketers, such as adult website operators offering many thousands of high resolution images, can use WebP to speed up their content delivery — while cutting costs and improving quality — making this technology an important one to watch.