Google Guetzli - a new open source JPEG encoder

Google Creates Guetzli, a New JPEG Encoder With 35 Percent Smaller Files Without Loss of Quality

And because humans are more sensitive to differences in brightness than color, JPEG also throws away some color information, rounding off color values and removing information that we probably won't miss.

WebP slashed file sizes by a quarter, but didn't always interact well with image-editing software, with Photoshop requiring a plugin, or with other browsers, which didn't all support the new file format.

Google has announced a new open source JPEG encoder called Guetzli that creates images with file sizes 35 percent smaller than now available methods.

Google scientists have developed a new way to compress JPEG images which makes them 35% smaller than is possible using existing compression methods, the company has announced on its Research Blog. Guetzli is very similar to Google's Zopfli algorithm, which creates smaller PNG and gzip files. As Google points our in its blogpost, WebP needs both client and ecosystem to change for the implementation. Below is a cropped image of a phone line. You can see an example of that in the image above, with the original uncompressed image on the left, the same one with the libjpeg encoder in the center, and one that used Guetzli on the right.

"Guetzli specifically targets the quantization stage in which the more visual quality loss is introduced, the smaller the resulting file".

The algorithm, dubbed Guetzil (that's Swiss German for cookie), is said to create smaller file sizes without sacrificing much in the way of quality. Google says this method "approximates color perception and visual masking in a more thorough and detailed way".

20 x 24 pixel zoomed areas from a picture of a cat's eye. However, Google said that images that use Guetzli are preferred visually over images that use libjpeg-based compression.

There is a slight downside (of sorts) for the new algorithm: it takes a little more time to compress, but the benefits outweigh the processing costs, as users are on the receiving end of the image - and needn't foot the CPU bill.

For Google's Guetzli speed boost, researchers developed a test called Butteraugli created to model human vision. While Guetzli's main use will be to reduce JPEG file size, Google Research recognizes that it will also use it to increase its quality.

Guetzil works by focusing on the quantization stage of the compression process.

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