XploRe Help : rgb2hls

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:	hls2rgb rgb2hls hls2rgb

Quantlet:		rgb2hls
Description:		converts an RGB colour vector into an HLS vector.

Usage:	`HLS=rgb2hls(RGB)`
Input:
	`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.
Output:
	`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.

Note:

The conversion of RGB into HLS colours can be useful for changing lightness (i.e. a plot can be made lighter or darker) or saturation (e.g. setting saturation S=0 will convert a colour plot into a greyscale one). The altered plot can be converted back into the RGB format with hls2rgb.xpl.

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