So far the results have been useful for me. It's been able to reduce size on some tougher images that other optimizers would ruin quality-wise.
Guetzli: A New Open-Source JPEG Encoder
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Re: Guetzli: A New Open-Source JPEG Encoder
#72As the author of the original libjpeg (back in 1991), I think this has been a long time coming! More power to Google.
Impressive :)
What are you on these days ? image codecs still ?
Re: Guetzli: A New Open-Source JPEG Encoder
#73I'll run some of my own experiments on this today, but I'm initially concerned about color muting. Specifically looking at the cat's eye example, in the bottom of the pupil area there's a bit of green (reflection?) in the lower pupil. In the original it is #293623 (green) - in the libjpeg it is #2E3230 (still green, slightly muted). But in the Guetzil encoded image it is #362C35 - still slightly green but quite close…
Agree, that difference is very striking side by side to me at least. Maybe not to everyone, but I hope they have some people with very good color perception on their team so they'll be able to see the difference.
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Re: Guetzli: A New Open-Source JPEG Encoder
#74I wonder, does google's blog pick up that I can't read their web page due to javascript blocking? Do they evaluate how many readers are turned away due to such issues?
Larry Page doesn't care, but it does keep Sergey up at night.
Re: Guetzli: A New Open-Source JPEG Encoder
#75I'm working on a similar thing ( http://getoptimage.com ). While Guetzli is still visually better and a bit smaller in file size, it's terribly slow and requires a lot of memory. But it's a great experiment. So much knowledge has been put into it. I believe using a full blown FFT and complex IQA metrics is too much. I have great results with custom quantization matrices, Mozjpeg trellis quantization, and a modificati…
Would it be possible to accelerate Guetzli on a GPU?
It appears that FFT can be GPU accelerated. Nvidia has cuFFT which claims to be 10x faster.
Re: Guetzli: A New Open-Source JPEG Encoder
#76The Github README says, "Guetzli generates only sequential (nonprogressive) JPEGs due to faster decompression speeds they offer." What's the current thinking on progressive JPEGs? Although I haven't noticed them recently, I don't know whether they're still widely used.
I don't really understand why they would be slower to decode. It's really just the same data ordered differently in the file.
I can see that if you try to render an incomplete file you might end up "wasting" effort blitting it to the screen and stuff before the rest of the data is decoded. But if thats a concern, one can simply rearrange the data back to scanline order and decode as normal?
Re: Guetzli: A New Open-Source JPEG Encoder
#77Is JPEG2000 with progressive/resolution-responsive transcoding still a thing or is HTML the way to go for responsive images (or maybe WepP)?
JPEG2000 died a bitter patent death.
Actually, it's alive and well in the form of embedded images in PDFs, where it's known as JPXFilter. Most of the ebooks (scans) I've downloaded from archive.org use it. If it didn't have any huge advantage I doubt they would've chosen it over standard JPEG.
The real problem, as far as I can see, is that JPEG2000 is really slow to decode due to its complexity.
Re: Guetzli: A New Open-Source JPEG Encoder
#78Earlier quoted context omitted.
So... machine learning? (Sorry for buzz-wording)
It is old school: 100000+ cpu hours of Nelder-Mead method (+common tricks) to match butteraugli to a set of 4000 human rated image pairs created with an earlier version of Guetzli and specially-built image distortion algorithms.
To those who didn't notice, that's one of the authors, well also took large part in previous related work.
Re: Guetzli: A New Open-Source JPEG Encoder
#79Great tech, shame about the name
Re: Guetzli: A New Open-Source JPEG Encoder
#80Earlier quoted context omitted.
So... machine learning? (Sorry for buzz-wording)
It is old school: 100000+ cpu hours of Nelder-Mead method (+common tricks) to match butteraugli to a set of 4000 human rated image pairs created with an earlier version of Guetzli and specially-built image distortion algorithms.
How did you protect against overfitting? How about local maxima? Some of your constants look surprising to say the least.
Most notably:
* The gamma value of 0.38 (when most studies suggest 1.5 - 2.5 for human eye gamma)
* The significant difference in the vertical and horizontal constants (when as far as I know human eyes are equally sensitive to most distortions independant of angle).