Google Guetzli – a new open source JPEG encoder

Google Guetzli is a new open source algorithm that creates high-quality JPEG images with file sizes 35% smaller than current methods.

The smaller images will enable web pages to load faster and use less data.

Guetzli produces smaller JPEG files and maintains compatibility with existing browsers, image processing applications, and the JPEG standard.

“This is similar to our Zopfli algorithm, which produces smaller PNG and gzip files without needing to introduce a new format,” said Google.

The quality of JPEG images is directly correlated to its multi-stage compression process: colour space transform, discrete cosine transform, and quantization.

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

Guetzli employs a search algorithm that tries to overcome the difference between the psychovisual modeling of JPEG’s format and Guetzli’s psychovisual model.

While Guetzli creates smaller image file sizes, the trade-off is that these search algorithms take longer to create compressed images.

20 x 24 pixel zoomed areas from a picture of a 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.


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Google Guetzli – a new open source JPEG encoder