Mathematically right values in decomposing to LAB ?

[snibgo (Alan Gibson)]

@Elle

@snibgo or @afre or other imagemagick experts - what command would be used to downsize using “binning” rather than the more usual downsizing while trying to preserve detail?

I’m not sure what you mean by “binning”.

Suppose we have four values (0, 1/3, 2/3 and 1), and we downsize by “binning” to two values. What are those values?

@Elle

Also, is there a way to tell imagemagick to not do any “gamma” correction?

IM won’t do any gamma correction unless you tell it to. There are a very small number of exceptions to this rule, and “-set colorspace sRGB” takes care of those. This operation doesn’t change pixel data, it only changes metadata, so IM won’t internally convert the image to sRGB.

Beware that some file formats can’t store gamma metadata, and for those formats that can, some software ignores it.

I guess that @MarionGaff1’s “no color correction” means the image is recorded as linear RGB, rather than non-linear sRGB. Testing with and without should answer that question.