Can I make changes to black-grey-white areas only?

[tahi.laci]

Eventually I want to make a script fu script so I can't just use fuzzy select tool or select by color. Basically I want to change the color curves for areas which are gray-scale, and leave alone anything colorful (red, blue, purple orange...) Is that possible?

If I could do it with a selection it would be even better because I might want to do the opposite later.

[rich2005]

I was thinking along the lines of this.

An image with a mix of colour and gray in it.


Decompose to CMYK and use the K channel as a layer mask on a duplicated layer


Then tweak that duplicated layer to adjust the gray bit.


Don't know how you would script it though.