sidef/scripts/Graphical/color_wheel.sf

#!/usr/bin/ruby

#
## https://rosettacode.org/wiki/Color_wheel
#

require('Imager')

var (width, height) = (300, 300)
var center = Complex(width/2 , height/2)

var img = %O<Imager>.new(xsize => width, ysize => height)

define(
    PI  = Num.pi,
    TAU = Num.tau,
)

for y=(^height), x=(^width) {
    var vector    = (center - x - y.i)
    var magnitude = (2*vector.abs / width)
    var direction = ((PI + atan2(vector.real, vector.imag)) / TAU)
    img.setpixel(x => x, y => y,
        color => Hash(hsv => [360*direction, magnitude, magnitude < 1 ? 1 : 0])
    )
}

img.write(file => 'color_wheel.png')