rgb2lab代码转换

rgb2lab代码转换

另外一个例子，来自：function [L,a,b] = RGB2Lab1(R,G,B)% function [L, a, b] = RGB2Lab(R, G, B)% RGB2Lab takes matrices corresponding to Red, Green, and Blue, and % transforms them into CIELab. This transform is based on ITU-R % Recommendation BT.709 using the D65 white point reference.% The error in transforming RGB -> Lab -> RGB is approximately% 10^-5. RGB values can be either between 0 and 1 or between 0 and 255. % By Mark Ruzon from C code by Yossi Rubner, 23 September 1997.% Updated for MATLAB 5 28 January 1998.if (nargin == 1) B = double(R(:,:,3)); G = double(R(:,:,2)); R = double(R(:,:,1));endif ((max(max(R)) > 1.0) | (max(max(G)) > 1.0) | (max(max(B)) > 1.0)) R = R/255; G = G/255; B = B/255;end[M, N] = size(R);s = M*N;% Set a thresholdT = 0.008856;RGB = [reshape(R,1,s); reshape(G,1,s); reshape(B,1,s)];% RGB to XYZMAT = [0.412453 0.357580 0.180423; 0.212671 0.715160 0.072169; 0.019334 0.119193 0.950227];XYZ = MAT * RGB;X = XYZ(1,:) / 0.950456;Y = XYZ(2,:);Z = XYZ(3,:) / 1.088754;XT = X > T;YT = Y > T;ZT = Z > T;fX = XT .* X.^(1/3) + (~XT) .* (7.787 .* X + 16/116);% Compute LY3 = Y.^(1/3); fY = YT .* Y3 + (~YT) .* (7.787 .* Y + 16/116);L = YT .* (116 * Y3 - 16.0) + (~YT) .* (903.3 * Y);fZ = ZT .* Z.^(1/3) + (~ZT) .* (7.787 .* Z + 16/116);% Compute a and ba = 500 * (fX - fY);b = 200 * (fY - fZ);L = reshape(L, M, N);a = reshape(a, M, N);b = reshape(b, M, N);if ((nargout == 1) | (nargout == 0)) L = cat(3,L,a,b);end

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