哈里斯特征检测不准确

Question

我已经实现了Harris特征检测算法，并且与使用Matlab的内置函数相比，结果不准确：corner（I，＆＃39; Harris＆＃39;）。任何想法为什么这样？或者我错过了什么？

我的代码结果：

  im=imread('D:\lena_256.pgm');
    im=im2double(im);
   % im = double(im(:,:,1));
    sigma = 2;k = 0.04;

    % derivative masks
    s_D = 0.7*sigma;
    x  = -round(3*s_D):round(3*s_D);
    dx = x .* exp(-x.*x/(2*s_D*s_D)) ./ (s_D*s_D*s_D*sqrt(2*pi));
    dy = dx';

    % image derivatives
    Ix = conv2(im, dx, 'same');
    Iy = conv2(im, dy, 'same');

    % sum of the Auto-correlation matrix
    s_I = sigma;
    g = fspecial('gaussian',max(1,fix(6*s_I+1)), s_I);
    Ix2 = conv2(Ix.^2, g, 'same'); % Smoothed squared image derivatives
    Iy2 = conv2(Iy.^2, g, 'same');
    Ixy = conv2(Ix.*Iy, g, 'same');

    % interest point response
      cim = (Ix2.*Iy2 - Ixy.^2) - k*(Ix2 + Iy2).^2; % Original Harris measure.
    %cim=(Ix2.*Iy2 - Ixy.^2)./(Ix2 + Iy2);  %   harmonic mean
    % find local maxima on 3x3 neighborgood
    [r,c,max_local] = findLocalMaximum(cim,3*s_I);

    % set threshold 1% of the maximum value
    t = 0.005*max(max_local(:));

    % find local maxima greater than threshold
    [r,c] = find(max_local>=t);

    % build interest points
    points = [r,c];

    figure, imshow(im),title('Harris Feature Points');
    hold on
    plot(points(:,1),points(:,2),'r*');


function [row,col,max_local] = findLocalMaximum(val,radius)

    mask = fspecial('disk',radius)>0;
    val2 = imdilate(val,mask);
    index = val==val2;
    [row,col] = find(index==1);
    max_local = zeros(size(val));
    max_local(index) = val(index);

end

使用内置corner（）函数的结果：