I have the following image:
I want to change the colors so that they match my own Xylophone. Since there are in-between colors at the borders, just selecting a color and filling the selected area with my target color is not viable because the in-between colors will stay unchanged. See here (zoomed in), original green color and blue-colored version:
So my preferred approach is to select a larger area that contains all the in-between colors and some black border and colorize that whole selection. That way the main color changes, the in-between colors change accordingly, and black stays black. There are a number of color changing options in GIMP like "color balance", "hue-chroma" or "colorize", and I tried all of them (i.e. the ones I could find in the Colors menu). But I could not find any one that allows me to specify a target color.
Here is my target color:
So I thought I could just type in my RGB values in one of these colorizing options, but I could not find any option that takes an RGB value as input. I tried taking the L-C-h values instead, assuming it is just a different way of specifying RGB values, and entered them in the option "hue-chroma":
But firstly the maximum Hue value in that option is 180, so I could not use my actual value of 281.5 and secondly, this does not look anything like I want it: I expect the black to stay black and only the colors to change. So I am obviously not using that coloring option as intended.
How can I change the color of a selected area so that
- a specified color (here green) turns into a target color (here blue)
- white, grey, black stay unchanged
- in-between colors change accordingly so that the newly colorized image is as smooth as the original ?
Note: I know that I could select the green area close to the black border, grow it a bit, feather it a bit, then fill the selection with my target color. That will also give smooth transitions. But since this depends a lot on exactly where the feathing starts and how far it goes, this is quite fiddly. I am looking for a more robust solution.