So for example I want the colors red, blue, and yellow in the 500x500 and the placement has to be random. I was looking at some posts and the documentation but couldn't really find it. With the image I'm going to convert it to a pygame surface using "pygame.image.fromstring".

it should be something like this but in 500x500 and the colors only should be randomized with red, blue and yellow, instead of all those random colors

CodePudding user response：

If you only want three colours (or any other number under 256) you should consider using a palette image where, rather than storing three bytes for the RGB values of each pixel, you store a single byte which is the index into a palette (or table) of 256 colours. It is much more efficient. See discussion

That takes 1ms on my Mac compared to 180ms for iterating over the pixels and choosing one of 3 RGB colours for each, and creates a 50kB palletised output file rather than the 120kB RGB output file you get with the other method.