There is nothing special about this shade of green that causes it to come from a codec issue. This green is what you get when you convert a 0-buffer from YUV to RGB. Depending on what colorspace you convert with it will be a slightly different shade.

You can play around with this yourself in imagemagick:

    dd if=/dev/zero of=zero.yuv bs=480 count=240
    convert -depth 8 -size 320x240 yuv:zero.yuv green.png

Conversion from YUV to RGB will be at one of the last steps of the image capture pipeline. Anything in between could wipe the buffer to 0s. It could be due to a simple bug in the image pipeline or it could be censorship. It tells you nothing.

When you click OPs link you get to the reddit thread where as an explanation they cite your very comment here on HN. And we've come full circle.

I don't think that's right.

Why would a codec problem, repeatably, affect images of a particular document, but not other images?

Note that in the OPs photo (https://imgur.com/a/SCHGo4N) it happens to every other image consistently. If you were shooting raw (with Pixel, not familiar with Xiaomi camera), it would save the raw and jpeg together. The gallery not being able to display the raw image results in the green image would be consistent with whats being shown.

FWIW the redmi note 8 pro main 64mp camera (it's a Samsung sensor shared by many phones) can shoot in raw but only with a gcam port, not with the default Xiaomi camera app.

Making a guess here, the envelope has a distinct shade of pink, which may trigger some processing. It looks like it is in "AI" mode, and who knows what "AI" does.

Yes indeed. This was a really common bug on iOS 13 beta, too.

@dang or other mods, can you change the title to be a little less inflammatory?