Lecture 8 Audio and Image signals filtering

2D Convolution by Matlab filter2 command

² LP

boy= imread('boy_gray.tif' ');

h= (1/9)*ones(3);

boy_lp=filter2(h,boy);

% boy 自動被轉成 double 去計算

figure; imshow(uint8(boy_lp))

% 仔細觀察，發現比原圖模糊（blurred）些

Note: Manual Calculation should be demonstrated!

Note: Try h= (1/25)*ones(5);

² HP （Edge Detection）

boy= imread('boy_gray.tif');

% h= [0 -1 0; -1 4 -1; 0 -1 0]; 效果極不明顯

h= [0 0 -1 0 0; 0 -1 -2 -1 0; -1 -2 16 -2 -1; 0 -1 -2 -1 0; 0 0 -1 0 0];

boy_hp=filter2(h,boy);

figure; imshow(uint8(boy_hp))

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