Google Reduces JPEG Image File Sizes by 35 Percent


The third image was compressed with Guetzli and has fewer digital artifacts, even though its file size is smaller than the libjepeg file. Guetzli is the Swiss German word for "cookie", and the Guetzli project was led by Google Research's Zurich office in Switzerland. These zoomed-in images show the original at left, Guetzli compression in the middle, and an alternative called libjpeg at right.

Secondly, Guetzli would seem set to have a significant resource footprint compared to the long-established image compression libraries now in use (mostly over Apache or other Linux-based frameworks).

This algorithm is basically an encoder which creates JPEG files of size 35% smaller than other image file creation methods. Smaller images enable webmasters to create web pages that load faster and use less data than web pages with larger images.

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Google Research has released details of its new and more efficient method for encoding JPEG images, promising to cut a third off JPEG image file-sizes with equal (or improved) appearance - but at the cost of greater time needed for compression, relative to the venerable libjpeg method that has been in use for decades. "Guetzli strikes a balance between minimal loss and file size by employing a search algorithm that tries to overcome the difference between the psycho-visual modelling of JPEG's format, and Guetzli's psycho visual model, which approximates colour perception and visual masking in a more thorough and detailed way than what is achievable by simpler colour transforms and the discrete cosine transform". Guetzli focuses on compression at the quantization stage as that is where more visual degeneration of the image occurs. Google describes the slower compression process as a "worthy tradeoff". It would be interesting to see if Guetzli scores a wider acceptance.

The only downside to Guetzli is that it's slower to encode JPEGs than with libjpeg. Right, Guetzli compression. Credit: Google.

According to Ars Technica, the encoder technically works by improving the quality of the JPEG images while keeping the size of the file constant. The company performed experiments where images of equal file size were shown to study participants who consistently prefered the imaged compressed using Guetzli. It also aims to enhance usability for graphic designer, in addition to aiding future research on video and image compression techniques.