This is not what we call computer graphics.
I used to create them by applying paint with a brush.
However, around 1986, I started to use a computer to support my work.
This is a program that I made for Masu Media, where you input the length and width of the canvas, and it prints a ruler with a scale that divides the length by a power of two.
Fix the output ruler to the four sides of the canvas, place the ruler according to its scale, and divide the canvas into sections as if making marks with a needle.
The next step after the division was to paint, and since the commercial acrylic paints would show through the underpainting, I made my own paints with a higher pigment concentration.