Color math and programming code examples

These are the formulas used by our Color Calculator to convert color data in different color spaces.
Each conversion formula is written as a "neutral programming function", easy to be translate in any specific programming language:

XYZ → Standard-RGB

//X, Y and Z input refer to a D65/2° standard illuminant.
//sR, sG and sB (standard RGB) output range = 0 ÷ 255

var_X = X / 100
var_Y = Y / 100
var_Z = Z / 100

var_R = var_X *  3.2406 + var_Y * -1.5372 + var_Z * -0.4986
var_G = var_X * -0.9689 + var_Y *  1.8758 + var_Z *  0.0415
var_B = var_X *  0.0557 + var_Y * -0.2040 + var_Z *  1.0570

if ( var_R > 0.0031308 ) var_R = 1.055 * ( var_R ^ ( 1 / 2.4 ) ) - 0.055
else                     var_R = 12.92 * var_R
if ( var_G > 0.0031308 ) var_G = 1.055 * ( var_G ^ ( 1 / 2.4 ) ) - 0.055
else                     var_G = 12.92 * var_G
if ( var_B > 0.0031308 ) var_B = 1.055 * ( var_B ^ ( 1 / 2.4 ) ) - 0.055
else                     var_B = 12.92 * var_B

sR = var_R * 255
sG = var_G * 255
sB = var_B * 255

clc;
close all;
clear all;
rgb = imread('lena.bmp');
subplot(2,3,1),imshow(rgb,'InitialMagnification','fit');title('原图像');
rgb =double(rgb);%双精度化(0-255)
x = 0.607*rgb(:,:,1)+0.174*rgb(:,:,2)+0.201*rgb(:,:,3);
x = mat2gray(x);%把矩阵转化为灰度图像
y = 0.299*rgb(:,:,1)+0.587*rgb(:,:,2)+0.114*rgb(:,:,3);
y = mat2gray(y);
z = 0.066*rgb(:,:,2)+0.117*rgb(:,:,3);
z = mat2gray(z);
xyz = cat(3,x,y,z);%把x，y，z连在一起
subplot(2,3,3),imshow(xyz);title('XYZ图像');
subplot(2,3,4),imshow(x);title('X图像');
subplot(2,3,5),imshow(y);title('Y图像');
subplot(2,3,6),imshow(z);title('Z图像');

运行结果：

注：Matlab中没有lena.bmp文件，可以从网上下载，此外imshow(rgb,'notruesize')在Matlab2012中不在支持应改为 imshow(rgb,'InitialMagnification','fit')。