Library: | graphic |
See also: | lab2rgb rgb2hls hls2rgb |
Quantlet: | rgb2lab | |
Description: | converts an RGB colour vector into an L*a*b* vector. |
Usage: | Lab=rgb2lab(RGB) | |
Input: | ||
Lab | (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. | |
n/a | (n x 3) array of L*a*b* colours assigned to n objects. L* that ranges from 0 for black to 100 for white corresponds to luminance. L*, a* and b* are non-negative. Not all L*a*b colours can be represented as RGB ones. |
library("xplore"); library("graphic"); R=255~0~0; G=0~255~0; B=0~0~255; white=255~255~255; black=0~0~0; LabR=rgb2lab(R); LabG=rgb2lab(G); LabB=rgb2lab(B); LabWhite=rgb2lab(white); LabBlack=rgb2lab(black); LabR; LabG; LabB; LabWhite; LabBlack; LabNonRepr1=0~1~1; This colour cannot be represented as RGB LabNonRepr2=100~1~1; This colour cannot be represented as RGB RGBNonRepr1=lab2rgb(LabNonRepr1); RGBNonRepr2=lab2rgb(LabNonRepr2); RGBNonRepr1; RGBNonRepr2;
L*, a* and b* values for red, green, blue, white and black and the RGB values for colours that are non-representable as RGB