Google's new JPEG encoder reduces file sizes by 35 percent

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As for the technology driving this open-source algorithm, Google says that the quality of JPEG images is directly related to its multi-stage compression process. The algorithm used by the company allows it to compress JPEGs by up to 35% more than now available methods. It is an open-sourced algorithm can also be used in an alternative way, that is, you can also use it for increasing the image quality while keeping the same file size.

Coming back to Guetzli, meaning "cookie" in Swiss German, this compression technique is quite similar to the Zopfli algorithm which is used to shrink PNG and gzip files without needing to introduce a new format. A comparison test of images created by Guetzli and the popular libjpeg JPEG generation library found human testers prefer the Guetzli images.

The benefit of using Guetzil, aside from the reduction in image size and barely-noticeable changes in image quality, is that the files it turns out remain compatible with existing browsers, image processing programs and the JPEG standard itself.

Google has come up with a new algorithm that aims at reducing the JPEG file size by 35%.

For Google's Guetzli speed boost, researchers developed a test called Butteraugli created to model human vision. Guetzli fiddles with two particular parts of JPEG compression - discrete cosine transform, which governs how details like object edges are recorded, and quantization, which governs which colors are preserved and which are sacrificed to cut file size. Another upside is that the transition to using Guetzli will happen quietly in the background without any disruption to that next image search you perform looking for cute cats. Alternatively, it's now possible to significantly improve the image quality of a file without raising its size. Right, Guetzli compression. Credit: Google. Last, we hope that the new explicitly psychovisual approach in Guetzli will inspire further image and video compression research.

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

The downside to this methodology is that compression takes significantly longer than now available methods.

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

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