Tuesday, June 17, 2014
Matlab simulation code for Harris Corner Point Detection
- % Harris detector
- % The code calculates
- % the Harris Feature Points(FP)
- %
- % When u execute the code, the test image file opened
- % and u have to select by the mouse the region where u
- % want to find the Harris points,
- % then the code will print out and display the feature
- % points in the selected region.
- % You can select the number of FPs by changing the variables
- % max_N & min_N
- load Imag;
- I =double(frame);
- %****************************
- imshow(frame);
- k = waitforbuttonpress;
- point1 = get(gca,'CurrentPoint'); %button down detected
- rectregion = rbbox; %%%return figure units
- point2 = get(gca,'CurrentPoint');%%%%button up detected
- point1 = point1(1,1:2); %%% extract col/row min and maxs
- point2 = point2(1,1:2);
- lowerleft = min(point1, point2);
- upperright = max(point1, point2);
- ymin = round(lowerleft(1));
- %%% Length and height of the bounded rectangle region
- ymax = round(upperright(1));
- xmin = round(lowerleft(2));
- xmax = round(upperright(2));
- %***********************************
- Aj=6;
- cmin=xmin-Aj; cmax=xmax+Aj; rmin=ymin-Aj; rmax=ymax+Aj;
- min_N=12;max_N=16;
- %%%%%%%%%%%%%%Interest Points%%%%%%%%%%%%%%%%%%
- sigma=2; Thrshold=20; r=6; disp=1;
- dx = [-1 0 1; -1 0 1; -1 0 1]; % The Mask
- dy = dx';
- %%%%%% Derivatives of Ix and Iy
- Ix = conv2(I(cmin:cmax,rmin:rmax), dx, 'same');
- Iy = conv2(I(cmin:cmax,rmin:rmax), dy, 'same');
- %%%%%% Gaussien Filter
- g = fspecial('gaussian',max(1,fix(6*sigma)), sigma);
- %%%%% Convulation of Ix2, Iy2,Ixy using Gaussian window
- Ix2 = conv2(Ix.^2, g, 'same');
- Iy2 = conv2(Iy.^2, g, 'same');
- Ixy = conv2(Ix.*Iy, g,'same');
- %%%%%%%%%%%%%% Compute the cornerness values
- k = 0.04;
- R11 = (Ix2.*Iy2 - Ixy.^2) - k*(Ix2 + Iy2).^2;
- R11=(1000/max(max(R11)))*R11;
- R=R11;
- ma=max(max(R));
- sze = 2*r+1;
- MX = ordfilt2(R,sze^2,ones(sze));
- R11 = (R==MX)&(R>Thrshold);
- count=sum(sum(R11(5:size(R11,1)-5,5:size(R11,2)-5)));
- %%%%% Find local maxima above some threshold to detect interest points
- loop=0;
- while (((count<min_N)|(count>max_N))&(loop<30))
- if count>max_N
- Thrshold=Thrshold*1.5;
- elseif count < min_N
- Thrshold=Thrshold*0.5;
- end
- R11 = (R==MX)&(R>Thrshold);
- count=sum(sum(R11(5:size(R11,1)-5,5:size(R11,2)-5)));
- loop=loop+1;
- end
- R=R*0;
- R(5:size(R11,1)-5,5:size(R11,2)-5)=R11(5:size(R11,1)-5,5:size(R11,2)-5);
- [r1,c1] = find(R);
- PIP=[r1+cmin,c1+rmin]
- %%%%%%%%%%%%%%%%%%%% Display
- Size_PI=size(PIP,1);
- for r=1: Size_PI
- I(PIP(r,1)-2:PIP(r,1)+2,PIP(r,2)-2)=255;
- I(PIP(r,1)-2:PIP(r,1)+2,PIP(r,2)+2)=255;
- I(PIP(r,1)-2,PIP(r,2)-2:PIP(r,2)+2)=255;
- I(PIP(r,1)+2,PIP(r,2)-2:PIP(r,2)+2)=255;
- end
- imshow(uint8(I))
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