Harris Corner Detector - MATLAB Code

Code:

A = imread(‘cameraman.jpg’);    %needs image file “cameraman.jpg”

If length(size(A))>2

A = rgb2gray(A);

end

dx = [-1 0 1; -1 0 1; -1 0 1];  %Derivative masks

Ix = filter2(dx,A);

dy = [1 1 1; 0 0 0; -1 -1 -1];

Iy = filter2(dy,A);

Ix2 = Ix.^2;                    %computing products of derivatives

Iy2 = Iy.^2;

Ixy = Ix.*Iy;

clear Ix;

clear Iy;

%applying gaussian filter on the computed value

g= fspecial('gaussian',[6 6],2);

Ix2 = filter2(g,Ix2);

Iy2 = filter2(g,Iy2);

Ixy = filter2(g,Ixy);

height = size(A,1);

width = size(A,2);

res = zeros(height,width);

R = zeros(height,width);

Rmax = 0;

for a = 1:height

for b = 1:width

C = [Ix2(a,b) Ixy(a,b);Ixy(a,b) Iy2(a,b)];

R(a,b) = det(C)-0.01*(trace(C))^2;

if R(a,b) > Rmax

Rmax = R(a,b);

end;

end;

end;

count = 0;

for a = 2:height-1

for b = 2:width-1

if R(a,b) > 0.1*Rmax && R(a,b) > R(a-1,b-1) && R(a,b) > R(a-1,b) && R(a,b) > R(a-1,b+1) && R(a,b) > R(a,b-1) && R(a,b) > R(a,b+1) && R(a,b) > R(a+1,b-1) && R(a,b) > R(a+1,b) && R(a,b) > R(a+1,b+1)

res(a,b) = 1;

count = count+1;

end;

end;

end;

[posc, posr] = find(res == 1);

count;

imshow(A);

hold on;

plot(posr,posc,'r.');

Output:

            Original Image                          Result

            Original Image                                             Result