[css-images] Gamma errors in image downscaling

A colleague brought this [1] to my attention, which seems to demonstrate an image scaling bug in pretty much every browser I tried the testcase [2] on. Furthermore, the results across UAs are inconsistent, which might indicate a standardization opportunity. I, myself, have noticed similar errors when scaling down certain patterns in the past, so stumbling on these issues is not that rare.
Applying different values to the image-rendering property seems to affect the results, but no value produces a correctly downscaled image (including the various properietary values…).

Shouldn’t image-rendering: crisp-edges fix this? Is there any spec violation here at all, or is that part of image scaling undefined? Any thoughts?

[1]: http://www.4p8.com/eric.brasseur/gamma.html
[2]: http://www.4p8.com/eric.brasseur/gamma_dalai_lama.html