How can I plot a density distribution colormap on a gray scale image of a sample with variable sample thickness?

I have grayscale images of a wood sample with variable thickness at different points along its width. I need to do a moisture distribution colormap on that scaled to different thicknesses as it is in the real sample. How do I do that?

[Image Analyst]

You forgot to attach the image. Also, show us some kind of output graph or image that is what you'd like to obtain, because I don't know exactly what "moisture distribution colormap on that scaled to different thicknesses" would look like.