- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- % Harris角点提取算法 %
- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- clear;
- ori_im = imread('arroyo-r.tiff'); % 读取图像
- % fx = [5 0 -5;8 0 -8;5 0 -5]; % 高斯函数一阶微分，x方向(用于改进的Harris角点提取算法)
- fx = [-2 -1 0 1 2]; % x方向梯度算子(用于Harris角点提取算法)
- Ix = filter2(fx,ori_im); % x方向滤波
- % fy = [5 8 5;0 0 0;-5 -8 -5]; % 高斯函数一阶微分，y方向(用于改进的Harris角点提取算法)
- fy = [-2;-1;0;1;2]; % y方向梯度算子(用于Harris角点提取算法)
- Iy = filter2(fy,ori_im); % y方向滤波
- Ix2 = Ix.^2;
- Iy2 = Iy.^2;
- Ixy = Ix.*Iy;
- clear Ix;
- clear Iy;
- h= fspecial('gaussian',[7 7],2); % 产生7*7的高斯窗函数，sigma=2
- Ix2 = filter2(h,Ix2);
- Iy2 = filter2(h,Iy2);
- Ixy = filter2(h,Ixy);
- height = size(ori_im,1);
- width = size(ori_im,2);
- result = zeros(height,width); % 纪录角点位置，角点处值为1
- R = zeros(height,width);
- Rmax = 0; % 图像中最大的R值
- for i = 1:height
- for j = 1:width
- M = [Ix2(i,j) Ixy(i,j);Ixy(i,j) Iy2(i,j)]; % auto correlation matrix
- R(i,j) = det(M)-0.06*(trace(M))^2; % 计算R
- if R(i,j) > Rmax
- Rmax = R(i,j);
- end;
- end;
- end;
- cnt = 0;
- for i = 2:height-1
- for j = 2:width-1
- % 进行非极大抑制，窗口大小3*3
- if R(i,j) > 0.01*Rmax && R(i,j) > R(i-1,j-1) && R(i,j) > R(i-1,j) && R(i,j) > R(i-1,j+1) && R(i,j) > R(i,j-1) && R(i,j) > R(i,j+1) && R(i,j) > R(i+1,j-1) && R(i,j) > R(i+1,j) && R(i,j) > R(i+1,j+1)
- result(i,j) = 1;
- cnt = cnt+1;
- end;
- end;
- end;
- [posc, posr] = find(result == 1);
- cnt % 角点个数
- imshow(ori_im);
- hold on;
- plot(posr,posc,'r+');
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