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from the just-use-a-photocopier-multiple-times dept.
Google has developed and open-sourced a new JPEG algorithm that reduces file size by about 35 percent—or alternatively, image quality can be significantly improved while keeping file size constant. Importantly, and unlike some of its other efforts in image compression (WebP, WebM), Google's new JPEGs are completely compatible with existing browsers, devices, photo editing apps, and the JPEG standard.
The new JPEG encoder is called Guetzli, which is Swiss German for cookie (the project was led by Google Research's Zurich office). Don't pay too much attention to the name: after extensive analysis, I can't find anything in the Github repository related to cookies or indeed any other baked good.
There are numerous ways of tweaking JPEG image quality and file size, but Guetzli focuses on the quantization stage of compression. Put simply, quantization is a process that tries to reduce a large amount of disordered data, which is hard to compress, into ordered data, which is very easy to compress. In JPEG encoding, this process usually reduces gentle colour gradients to single blocks of colour and often obliterates small details entirely.
The difficult bit is finding a balance between removing detail, and keeping file size down. Every lossy encoder (libjpeg, x264, lame) does it differently.
(Score: 2) by shortscreen on Monday March 20 2017, @08:50AM
1) JPEG is plenty old enough to not be patent-encumbered anymore
2) PNG's compression algorithm is "run it through PKZip." Not terribly innovative or ideal.
3) It's true that camera makers like to brag about pixels, but your allegation that the images are over-compressed is baloney. The fact is, camera makers are counting red, green, and blue pixels separately. So one red, one green, one blue... they count that as 3 pixels, even though on your monitor it is only one pixel. A 16MP camera outputs an image file that is 5000x3333 or so, but in reality 2/3rds of that data wasn't even captured, it had to be interpolated because each pixel on the camera sensor only sees one of the three color channels.