cmykToRgb function
Convert a CMYK color to RGB, where c, m, y, k values are in the range [0, 255]. Returns a list [r, g, b] with values in the range [0, 255].
Implementation
void cmykToRgb(num c, num m, num y, num k, List<int> rgb) {
c /= 255.0;
m /= 255.0;
y /= 255.0;
k /= 255.0;
rgb[0] = (255.0 * (1.0 - c) * (1.0 - k)).round();
rgb[1] = (255.0 * (1.0 - m) * (1.0 - k)).round();
rgb[2] = (255.0 * (1.0 - y) * (1.0 - k)).round();
}