2 ms·

The effects are quite different, since reducing total variation also reduces texture, which is important to perceived quality. Here's a direct comparison-- note

The effects are quite different, since reducing total variation also reduces texture, which is important to perceived quality. Here's a direct comparison-- note how knusperli retains slightly more detail instead of oversmoothing: https://mod.ifies.com/f/200710_lena_decode_comparison.png https://mod.ifies.com/f/200710_lena_decode_comparison.png

enriquto 6y ago
Good point. Unfortunately, the lena image is quite bad for comparison, there's almost no texture (except for the blue kerchief). I wonder what would happen for a heavily textured image; say, white noise. Would knusperly smooth it only along the block boundaries and leave it alone elsewhere?
ache7 6y ago
Use "-w 0.0" switch to jpeg2png, gives slightly sharper results. Also try with: https://github.com/ilyakurdyukov/jpeg-quantsmooth https://github.com/ilyakurdyukov/jpeg-quantsmooth with "-q6" (default setting without luma-aware chroma upsampling) My guess is that quantsmooth won't handle squares in the background well, but will be better at the edges (without excessive blurring). Update: I tested it, it's about 10% quality, jpeg-quantsmooth doesn't handle this quality. At 25% quality - result is fine, starting at 20% and less - not good. Perhaps the synthesis of all three projects combined into one (taking best of each) could give a great result. So then... jpeg2png: overblurs and slow knusperli: does only deblocking, not removes artifacts jpegqs: fails to deblock low frequencies (less 25% quality)
sjwright 6y ago
I wish people would stop using that image as an example. Not because of its content (what a stupid beat-up that was) but because the source file is of such terrible quality that it isn’t representative of the images we routinely handle today. And the extreme colour cast makes it useless for judging skin tones.
Terretta 6y ago
The jpeg2png should have noise (grain) simulated back.

enriquto 6y ago

Good point. Unfortunately, the lena image is quite bad for comparison, there's almost no texture (except for the blue kerchief). I wonder what would happen for a heavily textured image; say, white noise. Would knusperly smooth it only along the block boundaries and leave it alone elsewhere?

ache7 6y ago

Use "-w 0.0" switch to jpeg2png, gives slightly sharper results. Also try with: https://github.com/ilyakurdyukov/jpeg-quantsmooth https://github.com/ilyakurdyukov/jpeg-quantsmooth with "-q6" (default setting without luma-aware chroma upsampling) My guess is that quantsmooth won't handle squares in the background well, but will be better at the edges (without excessive blurring). Update: I tested it, it's about 10% quality, jpeg-quantsmooth doesn't handle this quality. At 25% quality - result is fine, starting at 20% and less - not good. Perhaps the synthesis of all three projects combined into one (taking best of each) could give a great result. So then... jpeg2png: overblurs and slow knusperli: does only deblocking, not removes artifacts jpegqs: fails to deblock low frequencies (less 25% quality)

sjwright 6y ago

I wish people would stop using that image as an example. Not because of its content (what a stupid beat-up that was) but because the source file is of such terrible quality that it isn’t representative of the images we routinely handle today. And the extreme colour cast makes it useless for judging skin tones.

Terretta 6y ago

The jpeg2png should have noise (grain) simulated back.