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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: 0) by Anonymous Coward on Monday March 20 2017, @02:20AM (1 child)
Because the Flying Spaghetti Monster demands all feature films are encoded with 12bit JPEG 2000 for theatrical release?
JPEG is better for delivery because PNG was designed as a (patent encumbered) GIF replacement for use with illustrations and graphics. PNG was never designed to replace JPEG for photographic images -- even if it is widely used in production workflows.
I compiled this google tool earlier in the week. If I am compressing images for the web, I will use this compressor. My brief test (from a a 1080p still PNG ~1.9M) was 340k for this compressor Vs. 304k for imagemagick convert (both default settings: im 92%, google 95%). When I reduced the quality for the Google compressor down to 85% (fine for the web) the image size was 181k. In my brief test, the compressor was visually lossless at 1:1 (on my image) whereas I could already see artifacts in this particular IM conversion.
Would that be 8 or 16 PNG as opposed to 14 bit raw (which most cameras are capable of) and are you aware of the differences (over 8bit JPEG) in storage requirements?
Why not build Google's new compressor and do the tests for yourself before commenting? You do not appear to understand this compressor is for delivery, click a news item and it could deliver a more pleasing image faster and at lower bandwidth cost to the user. This at the expense of affordable CPU time to the distributor.
(Score: 2) by maxwell demon on Monday March 20 2017, @08:19PM
You are aware that JPEG 2000 [wikipedia.org] is not the same format as JPEG, and also offers lossless compression?
The Tao of math: The numbers you can count are not the real numbers.