Has anyone implemented moravec corner detector in matlab??

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B.k Sumedha
B.k Sumedha 2015-5-20
回答： Ignacio Rocco 2019-11-14
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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采纳的回答

Thorsten
Thorsten 2015-5-20
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
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.

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更多回答（1 个）

Ignacio Rocco
Ignacio Rocco 2019-11-14
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

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