How to draw color circle?

[WojTec]

I want to draw circles like in attachment (RGB and RYB). I want to only know how to draw circle filled with some colors spectrum, routine for RYB values I already have.

[Medium]

What you deem to be RGB is actually drawn using HSV. (Have a look here, the upper right in the topmost image.) So you basically go through a bitmap pixel by pixel, determin the angle and distance to the bitmap's center pixel, and use these for hue and saturation respectively. Vaule is simply fixed at 1. It naturally becomes a circle, since distances > 1 from the center would result in invalid parameters for HSV anyways.

[freeway]

Solution with source code here http://www.efg2.com/Lab/Graphics/Colors/HSV.htm