20×24 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. Image and caption via Google
Google has announced the open source release of Guetzli, a new JPEG encoder able to reduce a JPEG’s file size by up to 35%, without any significant loss of quality. Per a study detailing the algorithm, Guetzli ‘aims to produce visually indistinguishable images at a lower bit-rate than other common JPEG encoders,’ including libjpeg. However, the study goes on to caution that the compression tool is ‘currently extremely slow.’
Google announced the new encoder on Thursday, detailing it as a proof-of-concept that can be freely used by webmasters and others to reduce the size of JPEG image files. The algorithm merges ‘advanced psychovisual models with lossy compression techniques,’ according to the study, to produce high-quality compressed images. It’s a different approach than that taken by other Google projects we’ve looked at recently like RAISR. Google expresses a desire to see future compression research that is inspired by Guetzli’s own psychovisual underpinnings.