Guetzli: A New Open Source JPEG Encoder From Google

Robert Obryk and Jyrki Alakuijala, of Google Research Europe:
At Google, we care about giving users the best possible online experience, both through our own services and products and by contributing new tools and industry standards for use by the online community. That’s why we’re excited to announce Guetzli, a new open source algorithm that creates high quality JPEG images with file sizes 35% smaller than currently available methods, enabling webmasters to create webpages that can load faster and use even less data. Guetzli [guɛtsli] — cookie in Swiss German — is a JPEG encoder for digital images and web graphics that can enable faster online experiences by producing smaller JPEG files while still maintaining compatibility with existing browsers, image processing applications and the JPEG standard. […] And while Guetzli produces smaller image file sizes without sacrificing quality, we additionally found that in experiments where compressed image file sizes kept constant that human raters consistently preferred the images Guetzli produced over libjpeg images, even when the libjpeg files were the same size or even slightly larger. We think this makes the slower compression a worthy tradeoff.
They’re not exaggerating. I installed Guetzli (via Homebrew) and it produces JPEGs that are about one-third smaller and yet look the same to my eyes. It’s a significant breakthrough for such a venerable image format. There is, of course, a catch. Image processing is really slow. It takes about 8 minutes for Guetzli to process a single iPhone camera image on my 5K iMac. That doesn’t mean Guetzli isn’t useful — it just isn’t useful in a user-facing context. If I ran a site that published photos, I’d hook it up in the background on the server hosting my images.

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