Google’s Guetzli reduces size of JPG files up to 35% without loss in quality

Google has developed and launched a new encoder named Guetzli. It’s an open source algorithm that allows you to reduce the size of JPG files by up to 35% while keeping the quality unchanged. Additionally, you can increase the image quality while leaving the size unchanged.

Guetzli will allow you high compression density at a good quality of the image. It can be immensely helpful for saving images for the website. Using it will make the website use less data and thus be faster to load.

The visual quality of JPEG images depends on multi-stage compression process: color space transform, discrete cosine transform, and quantization. Guetzli targets the quantization stage. Here, the more visual quality loss is introduced, the smaller is the resulting file. What Guetzli does is make a balance between minimal loss and file size. It reduces the image up to 35% in size, but it’s typically 20 to 30%.

Google has offered these sample images to show the new algorithm compared to an uncompressed image or an image compressed using the common libjpeg encoder.

A crop of a phone line against blue sky. The first image is uncompressed. The second is compressed with libjpeg. The third image was compressed with Guetzli and has fewer digital artifacts, even though its file size is smaller than the libjepeg file.

Google team did experiments where human raters compared compressed image file sizes compressed with Guetzli and as libjpeg images. The raters consistently preferred the images Guetzli produced over libjpeg.

A crop of a cat’s eye. The first image is uncompressed. The second image is encoded with libjpeg and the third image uses Guetzli.

If you think it’s worth a try, note that Guetzly is compatible with existing browsers, image processing applications, and the JPEG standard. Google has made it free for everyone to use, and you can find it on Github. If you prefer its results over libjpeg, it may be worth a shot for making your website faster and easier to load.

[via Gizmodo; image credits: Google]