I = imread('cameraman.tif');%讀入圖像
      I = double(I)/255; 
 T = dctmtx(8);%計算離散變換矩陣，返回結果為雙精度型
 B = blkproc(I,[8 8],'P1*x*P2',T,T');%實現圖像的顯示塊操作
 mask =[1 1 1 1 0 0 0 0
            1 1 1 0 0 0 0 0
            1 1 0 0 0 0 0 0
           1 0 0 0 0 0 0 0
            0 0 0 0 0 0 0 0
            0 0 0 0 0 0 0 0
            0 0 0 0 0 0 0 0
            0 0 0 0 0 0 0 0];
 B2 = blkproc(B,[8 8],'P1.*x',mask);
 I2 = blkproc(B2,[8 8],'P1*x*P2',T',T);
imshow(I), figure, imshow(I2)