Image degradation upon upload

tnt wrote 5 years ago: 3

I've noticed that images are being overcompressed upon upload, sometimes with noticeable visual degradation. For example original and "original untouched" (sic). Note the red parts of the image https://i.imgur.com/8ggjRYW.png (original is on the top). Which is weird because the file size actually became larger (orig. 44,052 bytes became 45,950 bytes upon uload), so it's a loss on both quality and storage space. Maybe a different algorithm could be implemented? Or rather "original untouched" should literally mean what it says.

gazza911 wrote 5 years ago: 1

Already heavily optimised uploads sometimes see a minor difference in the quality - I've also seen some myself.

From a technical standpoint, we could use an objective algorithm that uses 'Full-reference image quality assessment' (FR IQA) - essentially, for example PSNR & SSIM; these compare the two images to quantity the degradation and if it's below a certain threshold then we accept it.

However this would require time to be invested in getting it to work and determining a threshold.

P.S. "Original Untouched" here refers to the resolution.

david wrote 5 years ago: 2

We do store all the originals that you upload. When we upgrade to a newer version of our image libraries in the future, we'll re-process all resized versions :)

tnt wrote 5 years ago: 1

gazza911 wrote:
Already heavily optimised uploads sometimes see a minor difference in the quality - I've also seen some myself.
From a technical standpoint, we could use an objective algorithm that uses 'Full-reference image quality assessment' (FR IQA) - essentially, for example PSNR & SSIM; these compare the two images to quantity the degradation and if it's below a certain threshold then we accept it.
However this would require time to be invested in getting it to work and determining a threshold.
P.S. "Original Untouched" here refers to the resolution.

And the next logical step would be implementing NR-IQA for filtering out crappy images? :D

But sounds good if you guys could include this in your roadmap at some point.

david wrote:
We do store all the originals that you upload. When we upgrade to a newer version of our image libraries in the future, we'll re-process all resized versions :)

That's a good news :) Ok, then, I'll leave it in your capable hands :)