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in “ Tech news in brief ”,
March 17, 2017.

Google releases open source JPEG encoder

Cat's eye.

Uncompressed original on the left. Guetzli (on the right) shows less ringing artefacts than libjpeg (middle) without requiring a larger file size. © Google.

Google has developed and open-sourced a new JPEG algorithm that reduces file size by about 20–35% percent, while still maintaining compatibility with existing browsers, image processing applications and the JPEG standard. This new encoder is called Guetzli, which is Swiss German for cookie (the project was led by Google Research’s Zurich office). It uses a new psychovisual model—called Butteraugli—to work out which colours and details to keep, and which to throw away. Guetzli uses a large amount of memory (300MB of RAM per 1MPix of the input image) and while it creates smaller image file sizes, the tradeoff is that it takes significantly longer to create compressed images than currently available method (as libjpeg). The algorithm is designed to work on high-quality images (e.g. that haven’t been already compressed with other JPEG encoders). While it works on other images too, results will be poorer. Guetzli generates only sequential (nonprogressive) JPEGs due to faster decompression speeds they offer.

Ars Technica, “Google reduces JPEG file size by 35%.”

Google’s open source blog, “Announcing Guetzli: A New Open Source JPEG Encoder .”

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