Reported Auto adjust colors - strange behaviour

[BobbyB]

Hi there,
There is a photo in the annex. If you try auto adjust (shift+u) you receive strange result
I guess the algorithm has a bug and should be (somehow) improved. I have got similar photos and works fine, just this one bring strange result.

Have a nice day,
Bobby

[Mij]

Shift+u is Auto Color correct which is not what this image needs. Yes, it is a strange and unexpected effect but I think that should alert you to the fact that you are using the wrong feature.
Try using the simple Color corrections.. option (Shift +G) and increase the Gamma correction which is what this image needs, or if you want an automatic adjustment use the AltaLux plugin from Image >Effects.

[BobbyB]

Thx... I am not worried about the picture itself and I know shift+g. I was just surprised by this behavior and wanted to let know someone :-)
[but really thx for info about AltaLux - I don't know it till now...]

[Mij]

There is almost no color in your picture apart from the bright yellow date stamp. Auto Color tries to balance that by introducing the complementary blue color into the dark areas.
I blanked out the yellow date stamp and applied Auto color correct with quite different results. See attached corrected image.

[BobbyB]

I am sorry, I don't think so. You can try this: just cut another piece of the photo - even smaller and inside the black part of the cat - and the algorithm works fine...

[Mij]

Yes you are right. Even a tiny patch of black or white in the image lets it work OK. I still believe that it is the yellow text that is the problem. It appears to assume it to be the white level reference point.
I changed the text color to a saturated yellow (RGB 256,256,0) and one with a bit of blue in it (RGB 256,256,100). Try them to see what a difference it makes to the Auto color correct function.