给我一个基于matlab的harris角点检测代码

以下是一个基于MATLAB的Harris角点检测代码示例：

% 读取图像
img = imread('example.jpg');
gray = rgb2gray(img);

% 计算图像的x、y方向梯度
dx = [-1 0 1; -1 0 1; -1 0 1];
dy = dx';
Ix = conv2(double(gray), dx, 'same');
Iy = conv2(double(gray), dy, 'same');

% 计算每个像素的差异
w_size = 3;
sigma = 1;
R = zeros(size(gray));
for i = 1:size(gray, 1)
    for j = 1:size(gray, 2)
        M = zeros(2, 2);
        for u = -w_size:w_size
            for v = -w_size:w_size
                if i+u <= 0 || j+v <= 0 || i+u > size(gray,1) || j+v > size(gray,2)
                    continue;
                end
                M(1,1) = M(1,1) + Ix(i+u, j+v)^2;
                M(1,2) = M(1,2) + Ix(i+u, j+v)*Iy(i+u, j+v);
                M(2,1) = M(2,1) + Ix(i+u, j+v)*Iy(i+u, j+v);
                M(2,2) = M(2,2) + Iy(i+u, j+v)^2;
            end
        end
        R(i,j) = det(M) - 0.04*(trace(M)^2);
    end
end

% 非极大值抑制
threshold = 0.01*max(max(R));
R_nms = R;
for i = 2:size(gray,1)-1
    for j = 2:size(gray,2)-1
        if R_nms(i,j) < threshold
            continue;
        end
        if R_nms(i,j) > R_nms(i-1,j-1) && R_nms(i,j) > R_nms(i-1,j) && R_nms(i,j) > R_nms(i-1,j+1) && ...
           R_nms(i,j) > R_nms(i,j-1) && R_nms(i,j) > R_nms(i,j+1) && ...
           R_nms(i,j) > R_nms(i+1,j-1) && R_nms(i,j) > R_nms(i+1,j) && R_nms(i,j) > R_nms(i+1,j+1)
            continue;
        end
        R_nms(i,j) = 0;
    end
end

% 显示角点
[x,y] = find(R_nms > 0);
imshow(img);
hold on;
plot(y,x,'r+');

请注意，此代码示例仅用于说明如何实现Harris角点检测算法。在实际应用中，需要根据数据集的特点进行参数调整和优化。