語法: B = dct2(A) B = dct2(A,m,n) B = dct2(A,[m n]) 舉例 RGB = imread('autumn.tif'); I = rgb2gray(RGB); J = dct2(I); imshow(log(abs(J)),[]), colormap(jet(64)), colorbar J(abs(J) < 10) = 0; K = idct2(J)/255; imshow(K)