Where can I find algorithms for converting color into pattern fill options?

Question

Algorithms

Needed for printing, when the dot can only be black or white.
The classic (we reduce the resolution of the image by 2 times and now we have 4 shades of gray) is not suitable.
There are relatively large areas of the same color in the image.

I want them to be, for example, shaded inside in different directions, with different fill patterns.
For example, as in the picture below, different sizes of circles and the distance between them.

I am clarifying. At the entrance is a color picture. Those. at least poke your nose at a good algorithm for finding the boundaries of adjacent areas.

Answer 1

Not what I was looking for. The patterns didn't work.
Used dithering.
Image Dithering: Eleven Algorithms and Source Code
www.tannerhelland.com/4660/dithering-eleven-algori...

Answer 2

It seems to me that this particular picture can be translated into HSL, find areas by H, and then segment your fills using the same H. You can check in which thread of the graphic editor - poke a pipette into different areas of the same segment and see if the Hue will be different in HSL space.