Google shrinks photo sizes by 35 percent
- Author: Joey Payne Mar 18, 2017,
Mar 18, 2017, 0:56
Guetzli's files are smaller, yes, but it takes the encoder a bit longer than other compression methods to shrink images. Guetzli promises more compression, without users or developers having to adopt a new file format. The tech giant now hopes that their new open-source compression algorithm will enable users to reduce website load times and bandwidth costs. The development team says the overall approach is similar to the one used in Google's earlier Zopfli algotithm used to compress gzip files and PNG images, and shares little with the RAISR and WebP methods that require "ecosystem changes for compression gains at internet scale", a fancy way of saying they're new formats and need big changes to server and browser software. Left: The uncompressed original. According to Google, this makes the slower compression a "worthy tradeoff".
"The visual quality of JPEG images is directly correlated to its multi-stage compression process: colour space transform, discrete cosine transform, and quantization", wrote Google. Despite the increased time, Google's post assures that human raters preferred the images churned out by Guetzli. If that's not something you care about, you can head over to the Github destination instead and check out all the files, instructions on installing the tool, and the code necessary for using it. "However, while Guetzli creates smaller image file sizes, the tradeoff is that these search algorithms take significantly longer to create compressed images than now available methods", the company notes in a blog. Mozilla, maker of the Firefox web browser, began a project in 2014 called Mozjpeg created to improve on standard compression engines. The time between shots might be reduced if Guetzli compression is used.
For more details on the nitty-gritty of how Guetzli actually accomplishes the improved encoding (it apparently involves "psychovisual models") check out the Google Research Blog and the published paper on Guetzli. Right: Guetzli. Google claims that Guetzli has fewer artifacts without a larger file size. And although Google compared Guetzli to mozjpeg and another JPEG encoder called libjpeg, there are other options, too. The second image is encoded with libjpeg and the third image uses Guetzli.