I have about a hundred illustrations that I want to prepare for printing, and I am struggling to find the right pipeline to make the unpainted parts of the paper WHITE.
Using some form of edge detection is not enough because watercolors often have very soft gradients from 'no color' to 'color', so before I can clip off some level of gray to make it WHITE, I think, I need to remove the paper texture noise from the images while preserving as much of the color and the detail of the painting as possible.
The paintings' borders are often white, and therefore the image's 'white regions' also need to be WHITE or else when printing them on paper, they will appear greyish and horrible.
Yes I have found (2) related questions and have tried:
- TTF (from gimp-gmic)
- selective gaussian blur + levels (to crop off the white regions after they have been smoothed.
Main issue so far is that in low-contrast but still colored regions the detail is lost after the blurring, or appear blocky once I try to sharpen the image to regain some detail on the high-contrast areas. Also in order to blur away the largest paper shadows I have to set a high blur radius and that results some of the 'good' color details to be caught in the crossfire as you can see in the second image:
which is not all that bad (the white regions are WHITE), but:
- the colored regions have still some blurry paper pattern going on, which might look ugly once printed.
- Some of the smaller color splotches are nice and sharp, some others are inexplicably blurred out.
So I guess the question is: what can I do to improve this process, or is there another I should try?