img= imread('tiger.jpg');
[col,row]=meshgrid(1:size(img,2),1:size(img,1));
imgVec=[reshape(img(:,:,1),[],1) reshape(img(:,:,2),[],1) reshape(img(:,:,3),[],1) row(:)   col(:)];
[imgVecQ,imgVecC]=kmeans(double(imgVec),15);
imgVecQK=pdist2(double(imgVec(:,1:3)),double(imgVecC(:,1:3)));

[aa,indMin]=min(imgVecQK,[],2);
imgVecNewQ=imgVecC(indMin,1:3);  %quantizing

imgNewQ=img;
imgNewQ(:,:,1)=reshape(imgVecNewQ(:,1),size(img(:,:,1)));
imgNewQ(:,:,2)=reshape(imgVecNewQ(:,2),size(img(:,:,1)));
imgNewQ(:,:,3)=reshape(imgVecNewQ(:,3),size(img(:,:,1)));

imshow(img)
figure,imshow(imgNewQ,[]);