"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 now available methods, enabling webmasters to create webpages that can load faster and use even less data". Google said the breakthrough is the result of an algorithm that balances quality reductions and file size by searching for differences between JPEG and Guetzli representations of image data.
Google has several other projects to reduce image sizes on the web, including its Zopfli encoder (which similarly creates smaller PNG files without breaking format compatibility) and WebP (a new image format that supports both lossless and lossy compression for improved file sizes). To accomplish this, Guetzli trades visual quality for a smaller file size at the quantization stage of image compression. The name Guetzli means cookie in Swiss German.
"...we additionally found that in experiments where compressed image file sizes are 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", said Google. The algorithm used by the company allows it to compress JPEGs by up to 35% more than now available methods. "We think this makes the slower compression a worthy tradeoff". Compressing a photo to reduce its file size is simple, but maintaining its high quality at the same time is tricky.
Guetzli is a new JPEG encoder developed by Google and made available to the public as an open source tool.
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. Even though there are other third-party ways to compress an image, but Guetzli has its way to get the data in order first and then follow up the compression office.
Google is shrinking JPEG image files by 35% to help boost online page load times. Presumably Google are considering optimisations and rational solutions to speed up Guetzli's compression speed performance. It also aims to enhance usability for graphic designer, in addition to aiding future research on video and image compression techniques.