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Published 20 hours ago • verified publisher icon libvips

Identical pixel buffers generate different histograms

Open mathrick opened this issue 6 years ago • 3 comments

This is a follow-up to the issue reported in a comment at https://stackoverflow.com/questions/58500459.

The attached images have identical pixel buffers, but generate different values through scanline_checksum(). Interestingly enough, their on-disk form is different, with img1.png being 3115 bytes, and img2.png 3019.

img1.png: img1

img2.png: img2

Vips info:

  • pyvips 2.1.8, ABI mode
  • libvips 8.4.5, installed from ubuntu bionic package

mathrick avatar Nov 06 '19 23:11 mathrick

Just checked with 2.1.8 / 8.8.3 built in API mode, identical results.

mathrick avatar Nov 07 '19 03:11 mathrick

Nevermind, I just realised the stupid and obvious difference between these two. I'll get better examples uploaded.

mathrick avatar Nov 07 '19 04:11 mathrick

No problem, thanks for investigating this!

jcupitt avatar Nov 07 '19 07:11 jcupitt