5 ms·

"jpeg2png gives best results for pictures that should never be saved as JPEG. Examples are charts, logo's, and cartoon-style digital drawings." Interesting val

"jpeg2png gives best results for pictures that should never be saved as JPEG. Examples are charts, logo's, and cartoon-style digital drawings." Interesting value proposition. There may be equivalents for other misused file types/formats. The obvious one is the inverse case of photos saved as GIFs, but I imagine audio and text (eg. PDF malapropisms?) are possible too.

makapuf 6y ago
I d say the issue is the prpgram here, a compressor program might have heuristic to detect png-favored images vs photos. I cannot imagine we couldn't detect the easy cases reliably (because I'd say often images are more in a category or another). Crop the image to 64x64, try png and if the result is sufficiently small continue, else convert to jpg ?
dmitriid 6y ago
And then someone uploads this image to twitter/facebook, and it gets triply re-encoded and resized with the worst algorithms known to man :(
- BlackLotus89 6y ago
  https://mobile.twitter.com/NolanOBrien/status/1204557498990002176 https://mobile.twitter.com/NolanOBrien/status/12045574989900... twitter now doesn't cripple uploaded images, but tries to preserve all information except exiv data.
  - dmitriid 6y ago
    Kudos to Twitter! Now if only they stopped cropping images to rand()xrand() in timelines pretending they employ advanced ML algorithms to do so :)
    - fireattack 6y ago
      It's not random though. They likely show most contrasted area (with maybe some face detection).
      - dmitriid 6y ago
        That's what they claim. The result seems to be no better than rand() :)
  - deleted 6y ago
    [deleted]
jandrese 6y ago
I just tried it with a text heavy screenshot, a common scenario where the JPEG encoding produces a poor result with lots of speckle around each letter. The result is very good. The speckling is effectively eliminated without smearing the letters. JPEG Encoded, 25% quality: http://jubei.ceyah.org/overcompressed/crop-jpg.png http://jubei.ceyah.org/overcompressed/crop-jpg.png JPEG2PNG: http://jubei.ceyah.org/overcompressed/crop-converted.png http://jubei.ceyah.org/overcompressed/crop-converted.png
- indigo945 6y ago
  I find the text on the reference decoded image easier to read, despite the colorful speckles surrounding the words. JPEG2PNG doesn't smear the letters a lot, but does appear to slightly deform them. Consider the leading "a" in "add license, readme", whose upper half seems to be closer together after the JPEG2PNG run. However, now I'm wondering whether my impression that the reference decoded text is easier to read is a form of overfitting. I have spent the past 20 years reading low-quality JPEG screenshots on the internet, maybe the perceptual centers of my brain have developed an unblocking algorithm?
  - stordoff 6y ago
    That's a really interesting suggestion. I'm seeing something similar - the jpeg2png output looks cleaner and at first glance more pleasant to look at, but the reference seems both sharper and easier to read. It feels somehow more easier to ignore the more obvious flaws in the reference, and being used to them sounds like a plausible explanation to my layman ear.
- fireattack 6y ago
  Why the whole picture shifted? This can't be good
  - jandrese 6y ago
    They're both cropped out of a full screen grab.

makapuf 6y ago

I d say the issue is the prpgram here, a compressor program might have heuristic to detect png-favored images vs photos. I cannot imagine we couldn't detect the easy cases reliably (because I'd say often images are more in a category or another). Crop the image to 64x64, try png and if the result is sufficiently small continue, else convert to jpg ?

dmitriid 6y ago

And then someone uploads this image to twitter/facebook, and it gets triply re-encoded and resized with the worst algorithms known to man :(

BlackLotus89 6y ago
https://mobile.twitter.com/NolanOBrien/status/1204557498990002176 https://mobile.twitter.com/NolanOBrien/status/12045574989900... twitter now doesn't cripple uploaded images, but tries to preserve all information except exiv data.
- dmitriid 6y ago
  Kudos to Twitter! Now if only they stopped cropping images to rand()xrand() in timelines pretending they employ advanced ML algorithms to do so :)
  - fireattack 6y ago
    It's not random though. They likely show most contrasted area (with maybe some face detection).
    - dmitriid 6y ago
      That's what they claim. The result seems to be no better than rand() :)
- deleted 6y ago
  [deleted]

jandrese 6y ago

I just tried it with a text heavy screenshot, a common scenario where the JPEG encoding produces a poor result with lots of speckle around each letter. The result is very good. The speckling is effectively eliminated without smearing the letters. JPEG Encoded, 25% quality: http://jubei.ceyah.org/overcompressed/crop-jpg.png http://jubei.ceyah.org/overcompressed/crop-jpg.png JPEG2PNG: http://jubei.ceyah.org/overcompressed/crop-converted.png http://jubei.ceyah.org/overcompressed/crop-converted.png

indigo945 6y ago
I find the text on the reference decoded image easier to read, despite the colorful speckles surrounding the words. JPEG2PNG doesn't smear the letters a lot, but does appear to slightly deform them. Consider the leading "a" in "add license, readme", whose upper half seems to be closer together after the JPEG2PNG run. However, now I'm wondering whether my impression that the reference decoded text is easier to read is a form of overfitting. I have spent the past 20 years reading low-quality JPEG screenshots on the internet, maybe the perceptual centers of my brain have developed an unblocking algorithm?
- stordoff 6y ago
  That's a really interesting suggestion. I'm seeing something similar - the jpeg2png output looks cleaner and at first glance more pleasant to look at, but the reference seems both sharper and easier to read. It feels somehow more easier to ignore the more obvious flaws in the reference, and being used to them sounds like a plausible explanation to my layman ear.
fireattack 6y ago
Why the whole picture shifted? This can't be good
- jandrese 6y ago
  They're both cropped out of a full screen grab.