Adjust hue / saturation such that colour X becomes colour Y
I need to convert some stock icon imagery to a pre-existing colour scheme. The method for conversion is to simply adjust the image hue to the right level.
However all I have to go on is existing imagery that has already undergone the process. As such, I know that the muddy green of
99b963 should become the dull mauve of
My current method is trial and error: I zoom in to an area of green, overlay a layer featuring an adjacent pixel of the target mauve, select the original layer, then adjust saturation until it looks right. At that point I step out of the adjustment dialogue, get the color picker out, and compare. Repeat until just right.
Does Photoshop / Gimp / Paint.NET have a simpler, procedural method for achieving this, in 1 step if possible? If not, is there a less trial-and-error method to achieve the right hue given a target colour difference?
Does the "Replace Color" feature in Photoshop solve your problem?
Image > Adjustments > Replace Color
There you can select a color with the eyedropper which is then also displayed under the "Replacement" section. If you click on the color rectangle in this section the color picker dialog opens and you can specify a desired hue.
Adjust the effect with the "Fuzziness" slider.