[37] | 1 | % Demonstration of feature matching via simple correlation, and then using |
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| 2 | % RANSAC to estimate the homography matrix and at the same time identify |
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| 3 | % (mostly) inlying matches |
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| 4 | |
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| 5 | % Peter Kovesi |
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| 6 | % School of Computer Science & Software Engineering |
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| 7 | % The University of Western Australia |
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| 8 | % pk at csse uwa edu au |
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| 9 | % http://www.csse.uwa.edu.au/~pk |
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| 10 | % |
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| 11 | % February 2004 |
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| 12 | |
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| 13 | % Adapted to use vgg functions by Peter Kovesi and Andrew Zisserman |
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| 14 | |
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| 15 | function H = testhomog_vgg |
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| 16 | |
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| 17 | close all |
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| 18 | |
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| 19 | thresh = 500; % Harris corner threshold |
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| 20 | nonmaxrad = 3; % Non-maximal suppression radius |
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| 21 | dmax = 100; |
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| 22 | w = 11; % Window size for correlation matching |
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| 23 | |
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| 24 | im1 = rgb2gray(imread('keble.000.png')); |
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| 25 | im2 = rgb2gray(imread('keble.003.png')); |
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| 26 | |
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| 27 | % Find Harris corners in image1 and image2 |
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| 28 | [cim1, r1, c1] = harris(im1, 1, thresh, 3); |
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| 29 | show(im1,1), hold on, plot(c1,r1,'r+'); |
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| 30 | |
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| 31 | [cim2, r2, c2] = harris(im2, 1, thresh, 3); |
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| 32 | show(im2,2), hold on, plot(c2,r2,'r+'); |
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| 33 | |
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| 34 | drawnow |
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| 35 | |
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| 36 | tic |
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| 37 | [m1,m2] = matchbycorrelation(im1, [r1';c1'], im2, [r2';c2'], w, dmax); |
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| 38 | toc |
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| 39 | % Display putative matches |
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| 40 | show(im1,3), set(3,'name','Putative matches'), hold on |
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| 41 | for n = 1:length(m1); |
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| 42 | line([m1(2,n) m2(2,n)], [m1(1,n) m2(1,n)]) |
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| 43 | end |
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| 44 | |
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| 45 | % Assemble homogeneous feature coordinates for fitting of the |
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| 46 | % homography matrix, note that [x,y] corresponds to [col, row] |
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| 47 | x1 = [m1(2,:); m1(1,:); ones(1,length(m1))]; |
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| 48 | x2 = [m2(2,:); m2(1,:); ones(1,length(m1))]; |
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| 49 | |
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| 50 | t = .001; % Distance threshold for deciding outliers |
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| 51 | [H, inliers] = ransacfithomography_vgg(x1, x2, t); |
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| 52 | |
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| 53 | fprintf('Number of inliers was %d (%d%%) \n', ... |
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| 54 | length(inliers),round(100*length(inliers)/length(m1))) |
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| 55 | fprintf('Number of putative matches was %d \n', length(m1)) |
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| 56 | |
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| 57 | % Display both images overlayed with inlying matched feature points |
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| 58 | show(double(im1)+double(im2),4), set(4,'name','Inlying matches'), hold on |
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| 59 | plot(m1(2,inliers),m1(1,inliers),'r+'); |
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| 60 | plot(m2(2,inliers),m2(1,inliers),'g+'); |
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| 61 | |
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| 62 | % Step through each matched pair of points and display the |
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| 63 | % line linking the points on the overlayed images. |
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| 64 | |
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| 65 | for n = inliers |
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| 66 | line([m1(2,n) m2(2,n)], [m1(1,n) m2(1,n)],'color',[0 0 1]) |
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| 67 | end |
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| 68 | |
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| 69 | return |
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| 70 | |
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| 71 | |
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