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Advanced Image Optimization Tricks

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Re: Advanced Image Optimization Tricks

#21
post #12

Earlier quoted context omitted.

Well the whole point of a compression scheme like JPEG is to use what we know about human vision to minimize file size while not visually changing anything. But JPEG is a pretty crude algorithm designed mainly to be computationally cheap [to match the capabilities of computer hardware in 1992 when it was created]. Trying to make better encoders within the limits of what JPEG decoders can handle is quite limiting, and…

I'm trying to write a better JPEG compressor: https://github.com/pornel/jpeg-compressor IMHO JPEG algorithm isn't crude. IMHO it's actually quite brilliant—simple and very closely tied to human perception. The core concept of DCT quantization hasn't been beaten yet—even latest video codecs use it, just with tweaks on top like block prediction and better entropy coding. Wavelet compressors like JPEG 2000 beat JPEG onl…

I have tried your JPEG compressor. While it does make red less dull at 2x2 chroma subsampling, it does also blur red (or orange) into (white) backgrounds. IMO the sum is negative, at least with the particular image I tried.

I'm particularly interested in this because lossy WebP only supports 2x2 chroma subsampling. So any optimisation for JPEG could maybe also be applied to WebP.

I have made a topic about this once on the WebP group, which also has the image I tried with your compressor.

https://groups.google.com/a/webmproject.org/forum/#!topic/we...

Re: Advanced Image Optimization Tricks

#22
post #21
post #12

Earlier quoted context omitted.

I'm trying to write a better JPEG compressor: https://github.com/pornel/jpeg-compressor IMHO JPEG algorithm isn't crude. IMHO it's actually quite brilliant—simple and very closely tied to human perception. The core concept of DCT quantization hasn't been beaten yet—even latest video codecs use it, just with tweaks on top like block prediction and better entropy coding. Wavelet compressors like JPEG 2000 beat JPEG onl…

I have tried your JPEG compressor. While it does make red less dull at 2x2 chroma subsampling, it does also blur red (or orange) into (white) backgrounds. IMO the sum is negative, at least with the particular image I tried. I'm particularly interested in this because lossy WebP only supports 2x2 chroma subsampling. So any optimisation for JPEG could maybe also be applied to WebP. I have made a topic about this once o…

Thanks for trying it out.

With chroma subsampling there's tradeoff - either bleed black into color areas or bleed color outside. If have any ideas or know research on choosing when which option is best, then I'm all ears.

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