Convert RGB images to Gray Scale with Principle Component Analysis

Convert RGB to Gray using the function impca(image)

% This function uses principle component analysis to convert an RGB image
% to a gray scale image.
% Copyrighted by Tyler L. Coye

function [gray] = impca(im)
im = im2double(im);
lab = rgb2lab(im);
f = 0;
wlab = reshape(bsxfun(@times,cat(3,1-f,f/2,f/2),lab),[],3);
[C,S] = pca(wlab);
S = reshape(S,size(lab));
S = S(:,:,1);
gray = (S-min(S(:)))./(max(S(:))-min(S(:)));
end