Google Has a New Algorithm That Shrinks JPEGs by 35%

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

The new encoder is called Guetzli - Swiss German for "cookie", apparently - and according to Google, it can create "high quality JPEG images with file sizes 35 percent smaller than now available methods".

Smaller file sizes might seem an arcane technology concern, but they're crucial to fast-loading websites. The algorithm promises up to 35% more efficient compression of image files without the loss of image quality, when compared to existing compression algorithms.

Although there are several different ways to adjust the size and quality of a JPEG, Google's Guetzli (German for "cookie") is all about the "quantization stage of compression".

Robert Obryk and Jyrki Alakuijala, software engineers at Google Research Europe, highlight in a recent blog post that the algorithm tries to overcome the difference between the psychovisual modeling of JPEG's format and Guetzli's psychovisual model which approximates color perception and visual masking in a more thorough and detailed way than what is achievable by simpler color transforms and the discrete cosine transform. As compression increases, the file size reduces but more artifacts enter the image.

Images pushed through the Guetzli encoder are still available in a regular JPEG format, making them compatible with just about every application and browser now on the market. It would be interesting to see if Guetzli scores a wider acceptance.

According to Ars Technica, the encoder technically works by improving the quality of the JPEG images while keeping the size of the file constant.

Google has made the Guetzli encoder open source, and it's available on Github for anyone to integrate into their own projects or to use on their own. Those concerned with maintaining the utmost quality while conserving storage space or reducing upload times may want to give the tool a chance, though, as Google points to multiple tests that indicate its tool is more capable than libjpeg. However, Google said that images that use Guetzli are preferred visually over images that use libjpeg-based compression. It also aims to enhance usability for graphic designer, in addition to aiding future research on video and image compression techniques.

  • Fernando Stephens