XploRe Help : hls2rgb

Keywords - Function groups - @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Library:	graphic
See also:	rgb2hls rgb2lab lab2rgb

Quantlet:		hls2rgb
Description:		converts an HLS colour vector into an RGB vector.

Usage:	`RGB=hls2rgb(HLS)`
Input:
	`HLS`	(n x 3) array of HLS colours assigned to n objects. The values of the H (hue) channel range from 0 to 360. H=0 corresponds to pure red, H=120 to pure green and H=240 to pure blue. The values of the L (lightness) and S (saturation) channels range from 0 to 1.
Output:
	`n/a`	(n x 3) array of RGB colours assigned to n objects. The values of the R (red), G (green) and B (blue) channels range from 0 to 255.

Note:

The conversion of HLS into RGB colours can be useful for creating colouful plots in artificial simulated colour (temperature plots) instead of grey plots when the shades of grey represent a function value. To produce a plot in simulated colours you can fix L=0.5 and S=1 and let only H change in some range that lies within [0; 360].

Example:

library("xplore"); library("plot"); library("graphic"); nsteps=100; origin=#(-1, -1); endpoints=#(1, 1); steps=(endpoints-origin)/nsteps; npoints=#(nsteps+1, nsteps+1); A=grid(origin,steps,npoints); L=0.5*matrix((nsteps+1)*(nsteps+1),1); S=1*matrix((nsteps+1)*(nsteps+1),1); H=360*(A[,1]+A[,2])/(endpoints[1,1]-origin[1,1]+endpoints[2,1]-origin[2,1]); HLS=H~L~S; RGB=hls2rgb(HLS); createcolor(RGB); di=createdisplay(1,1); setmaskp(A, RGB, 7, 4); show(di, 1, 1, A);

Result:

A two dimensional plot. The simulated colours
change along a diagonal line.

Example:

library("xplore"); library("plot"); library("graphic"); points=colorcube(); hls2=rgb2hls(points.pcolor); rgb2=hls2rgb(hls2); new2=(hls2[,3].*cos((pi/180)*hls2[,1]))~hls2[,2]~(hls2[,3].*sin((pi/180)*hls2[,1])); new2=replace(new2,NaN,0); disp1=createdisplay(1,1); disp2=createdisplay(1,1); setmaskp(new2,points.pcolor,points.pstyle, 10); show(disp1,1,1,new2); setmaskp(rgb2,points.pcolor,points.pstyle, 10); show(disp2,1,1,rgb2);

Result:

HLS cone and RGB cube