Published: Sat, March 18, 2017
Science | By Boyd Webster

Google Guetzli - a new open source JPEG encoder

Google Guetzli - a new open source JPEG encoder

The third image was compressed with Guetzli and has fewer digital artifacts, even though its file size is smaller than the libjepeg file. More details at the link below.

The prize may be worth the effort: JPEG, long since the victor the image format wars of the late 1990s, now joins PNG in accounting for 73% of all content in websites - petabytes of data on a rolling basis, largely using technologies and standards which have not changed in almost twenty years.

In the example below, you can see the uncompressed original image on the left, libjpeg (another image compression tool) in the middle and Guetzli on the right. Smaller images enable webmasters to create web pages that load faster and use less data than web pages with larger images.

Google has developed a new open-source image compression algorithm that it says can reduce the size of JPEG images by 35 percent.

For Google's Guetzli speed boost, researchers developed a test called Butteraugli created to model human vision. Their Guetzli algorithm targets the quantization stage to reduce the size of image files by swapping it out for loss in visual quality. In other words, given two images of identical size, the Google-compressed JPEG looks nicer. You can view Guetzli's repository on GitHub here.

Google said its new algorithm will create "high quality JPEG images with file sizes 35 percent smaller than now available methods".

Guetzli employs a search algorithm that tries to overcome the difference between the psychovisual modeling of JPEG's format and Guetzli's psychovisual model. Alternatively, it's now possible to significantly improve the image quality of a file without raising its size.

Slower compression is likely to be an insignificant factor for desktop design environments, but has far bigger usage and resource ramifications for the millions of process threads which run every day over the internet, converting selfies, food shots and other user-generated content into optimised formats for viewing.

Note how the Guetzli compression on the right is smoother but lacks some richer colors of the libjpeg compression in the center.

Google says it asked people whether they preferred libjpeg-encoded JPEGs or Guetzli JPEGs and most picked the latter.

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