Has anyone implemented moravec corner detector in matlab??

Question

B.k Sumedha 2015-5-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/217714-has-anyone-implemented-moravec-corner-detector-in-matlab

回答： Ignacio Rocco 2019-11-14

采纳的回答： Thorsten

在 MATLAB Online 中打开

This is what i have tried.But with very less accurate.

clear all

close all

clc

tic

I=imread('panorama_image1.jpg');

originalmap=I;

w=5;

m=floor(size(I,1)/w);

n=floor(size(I,2)/w);

c=ceil(w/2)+(0:n-1)*w;

r=ceil(w/2)+(0:m-1)*w;

step=floor(w/2);

for y_unit=1:m

    for x_unit=1:n 
        v1=0;v2=0;v3=0;v4=0; 
        for i=-step:step-1 
            v1=v1+(I(r(y_unit),c(x_unit)+i)-I(r(y_unit),c(x_unit)+i+1))^2; 
            v2=v2+(I(r(y_unit)+i,c(x_unit)+i)-I(r(y_unit)+i+1,c(x_unit)+i+1))^2; 
            v3=v3+(I(r(y_unit)+i,c(x_unit))-I(r(y_unit)+i+1,c(x_unit)))^2; 
            v4=v4+(I(r(y_unit)-i,c(x_unit)+i)-I(r(y_unit)-i-1,c(x_unit)+i+1))^2; 
        end 
        IV_cr(y_unit,x_unit)=min([v1,v2,v3,v4]); 
    end 
end

exper_thr=20;

IV_cr(IV_cr<exper_thr)=NaN;

wf=9;

mf=floor(m/wf);

nf=floor(n/wf);

xc=[];

yc=[]; for y_unit=1:mf

    for x_unit=1:nf 
        [C,I]=max(IV_cr((y_unit-1)*wf+1:y_unit*wf,(x_unit-1)*wf+1:x_unit*wf))
        [C1,I1]=max(C); 
        IV_crch(y_unit,x_unit)=C1;
        row=I(I1); 
        col=I1; 
        crch_row(y_unit,x_unit)=(y_unit-1)*wf+row;
        crch_col(y_unit,x_unit)=(x_unit-1)*wf+col;
        yc=[yc,r((y_unit-1)*wf+row)];xc=[xc,c((x_unit-1)*wf+col)]; 
        IV_cr((y_unit-1)*wf+1:y_unit*wf,(x_unit-1)*wf+1:x_unit*wf)=NaN; 
        IV_cr((y_unit-1)*wf+row,(x_unit-1)*wf+col)=C1; 
    end 
end 
figure(1) 
imshow(originalmap)

figure(2)

plot(xc,yc,'*')

view(0,-90)

toc;

t=toc;

disp(['amount of time',num2str(t),'sec'])

figure(3)

imshow(originalmap)

hold on

plot(xc,yc,'R*')

axis on

end

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Answer 1

Thorsten 2015-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/217714-has-anyone-implemented-moravec-corner-detector-in-matlab#answer_179774

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I just did if for you:

function C = moravec(I)
%MORAVEC Moravec corner detector
%
%   C = MORAVEC(I)
%
%   Thorsten.Hansen@psychol.uni-giessen.de  2015-05-20
if nargin == 0 % simple test
  I = zeros(100);
  I(40:60, 40:60) = 1;
  C = moravec(I);
  imshow(0.5*C+I, [])
  if nargout == 0, clear C, end
  return
end
D(:,:,1) = diff([I I(:,end)]')';
D(:,:,2) = diff([I(:,1) I]')';
D(:,:,3) = diff([I; I(end,:)]);
D(:,:,4) = diff([I(1,:); I]);
C = sum(D.^2, 3);
if nargout == 0, clear C, end

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Thorsten 2015-5-20

编辑：Thorsten 2015-5-20

What do you mean by "Bad luck"? Does the result look strange, or do you get a Matlab error? The Moravec detector is highly sensitive to noise, so you get fine results for artificial images (run moravec without arguments to see an overlay of the image and the detected corners), but less so for natural images.

B.k Sumedha 2015-5-20

ok fyn

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Answer 2

Ignacio Rocco 2019-11-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/217714-has-anyone-implemented-moravec-corner-detector-in-matlab#answer_401570

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Hi,

Thanks Thorsten for your code! However I think it's missing a few details. I slightly modified the implementation according to the original text by Moravec [1980], and I think now it's producing much better results.

Here's the updated code.

function C = moravec(I)
%MORAVEC Moravec corner detector
%
%   C = MORAVEC(I)
%
%   Thorsten.Hansen@psychol.uni-giessen.de  2015-05-20
%   Ignacio.Rocco@inria.fr                  2019-11-14
if nargin == 0 % simple test
  I = zeros(100);
  I(40:60, 40:60) = 1;
  C = moravec(I);
  imshow(0.5*C+I, [])
  if nargout == 0, clear C, end
  return
end
D(:,:,1) = conv2(conv2(single(I),[1 -1],'same').^2,ones(3),'same');
D(:,:,2) = conv2(conv2(single(I),[1;-1],'same').^2,ones(3),'same');
D(:,:,3) = conv2(conv2(single(I),[1 0;0 -1],'same').^2,ones(3),'same');
D(:,:,4) = conv2(conv2(single(I),[0 1;-1 0],'same').^2,ones(3),'same');
C = min(D.^2,[], 3);
if nargout == 0, clear C, end