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Google Develops Algorithm That Reduces JPEG Size By 35 Percent, Images Will Still Look Good, Though

17 March 2017, 10:35 pm EDT By Carl Velasco Tech Times
Google has devised a new way to encode web images that’ll maintain the quality while reducing the file size by 35 percent. It’s called Guetzli, and Google has made it available to download for free.  ( Justin Sullivan | Getty Images )

Google has come up with a brand-new image compression algorithm it devised, the purpose of which is to reduce file size of JPEGs by 35 percent, without any noticeable or significant dips in image quality.

Google's Guetzli Image Encoder

An even more important aspect is the algorithm's compatibility with a range of browsers, devices, apps, and the JPEG standard. Unlike Google's other attempts in image compression such as WebP and WebM, the encoder in question, called Guetzli, or Swiss German for "Cookie," is versatile and will readily work in the aforementioned platforms.

Google Research's Zurich office helmed the project, and if some are pressed with its confectionery-themed original name, then don't be; Ars Technica's analysis didn't render any relation of Guetzli to cookies, or anything of the sort.

How Image Compression Works

There are several approaches to tweaking JPEG images in terms of quality and size, but what Guetzli specifically targets is the quantization phase of image compression wherein there is more loss in terms of visual quality. In a nutshell, this process aims to reduce huge amounts of hard-to-compress disordered data into easy-to-compress ordered data. In typical JPEG encoding systems, this usually involves switching color gradients to single color blocks altogether or eliminating small details on a picture.

In compression, the tradeoff of keeping file sizes relatively small is sacrificing image quality. The trick is for compression systems to strike a balance between reducing the file size while keeping visual integrity regardless of detail removal. Every lossy encoder, as noted by Ars Technica, takes on it with different approaches, and in the case of Guetzli, Google says it does exactly this form of balance.

How Guetzli Approaches Image Compression

Guetzli, in this case, uses a psychovisual — a fancy term to denote the human vision processing system — model called Butteraugli to determine which colors and details to retain, and which to discard. Basically, the model "approximates colour perception and visual masking in a more thorough and detailed way" than other models.

From left to right: Original uncompressed image, libjpeg-encoded image, and Guetzli-encoded image.
(Photo : Google) From left to right: Original uncompressed image, libjpeg-encoded image, and Guetzli-encoded image.

How Google developed such a model remains privy to the company at present, although it's seemingly aided by computer-generated technology. Of course, Google is known for its predisposition to rely on neural networks and machine learning: perhaps these two advanced intelligent systems had a hand in the Guetzli's development.

Google says that while the new algorithm will primarily be used for reducing file size of JPEGs, it can also be leveraged to increase the perceived quality of images while keeping the file size the same. Impressively, when compared to another encoder, Google says that 75 percent were in favor of Guetzli, which indicates that Butteraugli, the psychovisual model, "reasonably" parallels human visual perception.

Google's new encoder is completely free and available to download on GitHub, so developers can start trying their hands on it. It's worth noting, however, that Guetzli encoding process is comparably slower to that of other encoders because of its quantization process. Its compatibility with a number of browsers, devices and such, however, should be its saving grace.

"It is our hope that webmasters and graphic designers will find Guetzli useful and apply it to their photographic content, making users' experience smoother on image-heavy websites in addition to reducing load times and bandwidth costs for mobile users," wrote Google in a blog post.

Zoom And Enhance

Guetzli isn't the only experiment Google has outed in terms of improving images on the web. In early February it devised a new fancy software that could turn pixelated images into detailed ones, basically the incarnate of the famed TV trope "Now zoom and enhance."

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