3 ms·

I am surprised that it survives twitter's image compression. I'm not familiar with JPEG format, but I'm familiar with PNG. I guess it's using some zlib-compress

I am surprised that it survives twitter's image compression. I'm not familiar with JPEG format, but I'm familiar with PNG. I guess it's using some zlib-compressed EXIF-like metadata field, seeing as ZIP also uses DEFLATE/zlib/whatever?

Retr0id 4y ago
It's embedded within an ICC colour profile, and therefore doesn't get touched by any image compression/resizing logic.
- Y-bar 4y ago
  Some eager image compression techniques will strip metadata including profiles (e. g. ImageOptim: https://imageoptim.com/color-profiles.html https://imageoptim.com/color-profiles.html) But generally you are correct.
  - Retr0id 4y ago
    any image compression/resizing logic [in twitter.com] [in 2018]
- csdvrx 4y ago
  How would do that nicely and automatically, to do funny things like that in a way that would be resistant to the accidental optimizations/resizing that will be applied to the JPG?
charonn0 4y ago
It's a polyglot file. JPEG decoders will ignore data that comes after the end-of-data marker, while zip decoders ignore data that comes before the first archive entry. Essentially, they ran `cat pic.jpg arch.zip > output.jpg`.