ipoint.cpp

#include "ipoint.h"

//! Populate IpPairVec with matched ipts 
void getMatches(IpVec &ipts1, IpVec &ipts2, IpPairVec &matches)
{
	float dist, d1, d2;
	OpenSurfInterestPoint *match;

	matches.clear();

	for(unsigned int i = 0; i < ipts1.size(); i++) 
	{
		d1 = d2 = FLT_MAX;

		for(unsigned int j = 0; j < ipts2.size(); j++) 
		{
			dist = ipts1[i] - ipts2[j];  

			if(dist<d1) // if this feature matches better than current best
			{
				d2 = d1;
				d1 = dist;
				match = &ipts2[j];
			}
			else if(dist<d2) // this feature matches better than second best
			{
				d2 = dist;
			}
		}

		// If match has a d1:d2 ratio < 0.65 ipoints are a match
		if(d1/d2 < 0.65) 
		{ 
			// Store the change in position
			ipts1[i].dx = match->x - ipts1[i].x; 
			ipts1[i].dy = match->y - ipts1[i].y;
			matches.push_back(std::make_pair(ipts1[i], *match));
		}
	}
}

//
// This function uses homography with CV_RANSAC (OpenCV 1.1)
// Won't compile on most linux distributions
//

//-------------------------------------------------------

//! Find homography between matched points and translate src_corners to dst_corners
int translateCorners(IpPairVec &matches, const CvPoint src_corners[4], CvPoint dst_corners[4])
{
#ifndef LINUX
	double h[9];
	CvMat _h = cvMat(3, 3, CV_64F, h);
	std::vector<CvPoint2D32f> pt1, pt2;
	CvMat _pt1, _pt2;

	int n = (int)matches.size();
	if( n < 4 ) return 0;

	// Set vectors to correct size
	pt1.resize(n);
	pt2.resize(n);

	// Copy Ipoints from match vector into cvPoint vectors
	for(int i = 0; i < n; i++ )
	{
		pt1[i] = cvPoint2D32f(matches[i].second.x, matches[i].second.y);
		pt2[i] = cvPoint2D32f(matches[i].first.x, matches[i].first.y);
	}
	_pt1 = cvMat(1, n, CV_32FC2, &pt1[0] );
	_pt2 = cvMat(1, n, CV_32FC2, &pt2[0] );

	// Find the homography (transformation) between the two sets of points
	if(!cvFindHomography(&_pt1, &_pt2, &_h, CV_RANSAC, 5))  // this line requires opencv 1.1
		return 0;

	// Translate src_corners to dst_corners using homography
	for(int i = 0; i < 4; i++ )
	{
		double x = src_corners[i].x, y = src_corners[i].y;
		double Z = 1./(h[6]*x + h[7]*y + h[8]);
		double X = (h[0]*x + h[1]*y + h[2])*Z;
		double Y = (h[3]*x + h[4]*y + h[5])*Z;
		dst_corners[i] = cvPoint(cvRound(X), cvRound(Y));
	}
#endif
	return 1;
}