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Seo Master present to you:

Urvang

Vikas

Jyrki

By Jyrki Alakuijala, Vikas Arora, and Urvang Joshi, Software Engineers, WebP Team

Cross-posted with the Chromium Blog

In September 2010 we announced the WebP image format with lossy compression. WebP was proposed as an alternative to JPEG, with 25–34% better compression compared to JPEG images at equivalent SSIM index. We received lots of feedback, and have been busy improving the format. Last month we announced WebP support for animation, ICC profile, XMP metadata and tiling. Today, we introduce a new mode in WebP to compress images losslessly, and support for transparency – also known as alpha channel – in both the lossless and lossy modes.

With these new modes, you can now use WebP to better compress all types of images on the web. 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. Animations compressed as GIFs can use animation support in WebP.

New lossless mode

Our main focus for lossless mode has been in compression density and simplicity in decoding. On average, we get a 45% reduction in size when starting with PNGs found on the web, and a 28% reduction in size compared to PNGs that are re-compressed with pngcrush and pngout. Smaller images on the page mean faster page loads.

New transparency mode

Today, webmasters who need transparency must encode images losslessly in PNG, leading to a significant size bloat. WebP alpha encodes images with low bits-per-pixel and provides an effective way to reduce the size of such images. Lossless compression of the alpha channel adds just 22% bytes over lossy (quality 90) WebP encoding. Smaller alpha overhead means richer images on webpages.

You can find a more detailed compression study for these modes here and sample images in the WebP-Gallery. The bit stream specification has not been finalized, and the encoding and decoding implementations have not yet been optimized for processing speed. We encourage you to try it out on your favorite set of images, check out the code, and provide feedback. We hope WebP will now handle all your needs for web images, and we're working to get WebP supported in more browsers.


Dr. Jyrki Alakuijala is a Software Engineer with a special interest in data compression. He is a father of five daughters, and sings in the Finnish Choir in Zürich. Before joining Google, Jyrki worked in neurosurgical and radiotherapy development.

Vikas Arora is a Software Engineer with a special interest in signal processing and data compression. Before joining Google, Vikas worked in the VLSI domain developing digital and analog signal simulators.

Urvang Joshi is a Software Engineer, especially interested in image processing, machine learning, and computer vision. He is also a table tennis and chess enthusiast.

Posted by Scott Knaster, Editor

2013, By: Seo Master

Seo Master present to you: By Jyrki Alakuijala, WebP Team

At Google, we are constantly looking at ways to make web pages load faster. One way to do this is by making web images smaller. This is especially important for mobile devices where smaller images save both bandwidth and battery life. Earlier this month, we released version 0.2 of the WebP library that adds support for lossless and transparency modes to compress images. This version provides CPU and memory performance comparable to or better than PNG, yet results in 26% smaller files.

WebP’s improved compression comes from advanced techniques such as dedicated entropy codes for different color channels, exploiting 2D locality of backward reference distances and a color cache of recently used colors. This complements basic techniques such as dictionary coding, Huffman coding and color indexing transform. We think that we've only scratched the surface in improving compression. Our newly added support for alpha transparency with lossy images promises additional gains in this space, helping make WebP an efficient replacement for PNG.

The new WebP modes are supported natively in the latest Beta version of Chrome. The bit stream specification for these new WebP modes has been finalized and the container specification has been updated. We thank the community for their valuable feedback and for helping us evolve WebP as a new image compression format for the web. We encourage you to try these new compression methods on your favorite set of images, check out the code, and continue to provide feedback.

Dr. Jyrki Alakuijala is a Software Engineer with a special interest in data compression. He is a father of five daughters, and sings in the Finnish Choir in Zürich. Before joining Google, Jyrki worked in neurosurgical and radiotherapy development.

Posted by Ashleigh Rentz, Editor Emerita

2013, By: Seo Master