% Demonstration of feature matching via simple correlation, and then using% RANSAC to estimate the homography between two images and at the same time% identify (mostly) inlying matches%% Usage:  testhomog              - Demonstrates homography calculation on two %                                  default images%         testhomog(im1,im2)     - Computes homography on two supplied images%% Edit code as necessary to tweak parameters% Copyright (c) 2004-2005 Peter Kovesi% School of Computer Science & Software Engineering% The University of Western Australia% http://www.csse.uwa.edu.au/% % Permission is hereby granted, free of charge, to any person obtaining a copy% of this software and associated documentation files (the "Software"), to deal% in the Software without restriction, subject to the following conditions:% % The above copyright notice and this permission notice shall be included in % all copies or substantial portions of the Software.%% The Software is provided "as is", without warranty of any kind.% February 2004% August   2005 Octave compatibilityfunction testhomog(im1,im2)    if nargin == 0	im1 = imread('boats.tif');	im2 = imread('boatsrot.tif');        end        close all        v = version; Octave=v(1)<'5';  % Crude Octave test    thresh = 500;   % Harris corner threshold    nonmaxrad = 3;  % Non-maximal suppression radius    dmax = 50;    w = 11;         % Window size for correlation matching        % Find Harris corners in image1 and image2    [cim1, r1, c1] = harris(im1, 1, thresh, 3);    show(im1,1), hold on, plot(c1,r1,'r+');    [cim2, r2, c2] = harris(im2, 1, thresh, 3);    show(im2,2), hold on, plot(c2,r2,'r+');    drawnow    [m1,m2] = matchbycorrelation(im1, [r1';c1'], im2, [r2';c2'], w, dmax);    % Display putative matches    show(im1,3), set(3,'name','Putative matches'),     if Octave, figure(1); title('Putative matches'), axis('equal'), end        for n = 1:length(m1);	line([m1(2,n) m2(2,n)], [m1(1,n) m2(1,n)])    end    % Assemble homogeneous feature coordinates for fitting of the    % homography, note that [x,y] corresponds to [col, row]    x1 = [m1(2,:); m1(1,:); ones(1,length(m1))];    x2 = [m2(2,:); m2(1,:); ones(1,length(m1))];            t = .001;  % Distance threshold for deciding outliers    [H, inliers] = ransacfithomography(x1, x2, t);    fprintf('Number of inliers was %d (%d%%) \n', ...	    length(inliers),round(100*length(inliers)/length(m1)))    fprintf('Number of putative matches was %d \n', length(m1))                % Display both images overlayed with inlying matched feature points    if Octave	figure(4); title('Inlying matches'), axis('equal'),     else        show(im1,4), set(4,'name','Inlying matches'), hold on    end            plot(m1(2,inliers),m1(1,inliers),'r+');    plot(m2(2,inliers),m2(1,inliers),'g+');        for n = inliers	line([m1(2,n) m2(2,n)], [m1(1,n) m2(1,n)],'color',[0 0 1])    end