Draws a HSV/HSB chromatic disk. chromac(xc,yc,rmax,ds,dv,tred) with : - xc and yc : center at coordinates - rmax : radius - ds and dv : * 0 to keep S or V to 1 * 1 to have S or V increase from 0 in the center to 1 * -1 to have S or V decrease from 1 in the center to 0 - tred : position in radians of the red component on the disk (0=right, pi/2=top, …) - rev : True or False to to revert the color order