I made this algorithm in 2017(https://www.reddit.com/r/proceduralgeneration/comments/6mta0f/watercolor_simple_noise_algorithm). And recently I revisited, and made it smoother.

Features
- color: 90%, b/w: 10%
- filter
- lighter: 40% (white edge)
- difference: 40% (black edge)
- screen: 15% (white edge, but more natural)
- none: 5% (original algorithm)

hit [s] for save 1024 x 1024 px image.

* I used Sobel filter implementation from https://github.com/miguelmota/sobel