rgb=imread('lily.tif'); 
imshow(rgb);
title('原始圖像');
[X_no_dither,map]=rgb2ind(rgb,8,'nodither');
[X_dither,map]=rgb2ind(rgb,8,'dither');
figure, imshow(X_no_dither,map);
title('沒有抖動的變換圖像');
figure, imshow(X_dither,map);
title('抖動過變換圖像');