match.c

Rob Hess Linux下的SIFT提取源码

/*
  Detects SIFT features in two images and finds matches between them.

  Copyright (C) 2006-2007  Rob Hess <[e-mail]>

  @version 1.1.1-20070913
*/

#include "sift.h"
#include "imgfeatures.h"
#include "kdtree.h"
#include "utils.h"
#include "xform.h"

#include <cv.h>
#include <cxcore.h>
#include <highgui.h>

#include <stdio.h>


/* the maximum number of keypoint NN candidates to check during BBF search */
#define KDTREE_BBF_MAX_NN_CHKS 200

/* threshold on squared ratio of distances between NN and 2nd NN */
#define NN_SQ_DIST_RATIO_THR 0.49


int main( int argc, char** argv )
{
  IplImage* img1, * img2, * stacked;
  struct feature* feat1, * feat2, * feat;
  struct feature** nbrs;
  struct kd_node* kd_root;
  CvPoint pt1, pt2;
  double d0, d1;
  int n1, n2, k, i, m = 0;

  if( argc != 3 )
    fatal_error( "usage: %s <img1> <img2>", argv[0] );
  
  img1 = cvLoadImage( argv[1], 1 );
  if( ! img1 )
    fatal_error( "unable to load image from %s", argv[1] );
  img2 = cvLoadImage( argv[2], 1 );
  if( ! img2 )
    fatal_error( "unable to load image from %s", argv[2] );
  stacked = stack_imgs( img1, img2 );

  fprintf( stderr, "Finding features in %s...\n", argv[1] );
  n1 = sift_features( img1, &feat1 );
  fprintf( stderr, "Finding features in %s...\n", argv[2] );
  n2 = sift_features( img2, &feat2 );
  kd_root = kdtree_build( feat2, n2 );
  for( i = 0; i < n1; i++ )
    {
      feat = feat1 + i;
      k = kdtree_bbf_knn( kd_root, feat, 2, &nbrs, KDTREE_BBF_MAX_NN_CHKS );
      if( k == 2 )
	{
	  d0 = descr_dist_sq( feat, nbrs[0] );
	  d1 = descr_dist_sq( feat, nbrs[1] );
	  if( d0 < d1 * NN_SQ_DIST_RATIO_THR )
	    {
	      pt1 = cvPoint( cvRound( feat->x ), cvRound( feat->y ) );
	      pt2 = cvPoint( cvRound( nbrs[0]->x ), cvRound( nbrs[0]->y ) );
	      pt2.y += img1->height;
	      cvLine( stacked, pt1, pt2, CV_RGB(255,0,255), 1, 8, 0 );
	      m++;
	      feat1[i].fwd_match = nbrs[0];
	    }
	}
      free( nbrs );
    }

  fprintf( stderr, "Found %d total matches\n", m );
  display_big_img( stacked, "Matches" );
  cvWaitKey( 0 );

  /* 
     UNCOMMENT BELOW TO SEE HOW RANSAC FUNCTION WORKS
     
     Note that this line above:
     
     feat1[i].fwd_match = nbrs[0];
     
     is important for the RANSAC function to work.
  */
  /*
  {
    CvMat* H;
    H = ransac_xform( feat1, n1, FEATURE_FWD_MATCH, lsq_homog, 4, 0.01,
		      homog_xfer_err, 3.0, NULL, NULL );
    if( H )
      {
	IplImage* xformed;
	xformed = cvCreateImage( cvGetSize( img2 ), IPL_DEPTH_8U, 3 );
	cvWarpPerspective( img1, xformed, H, 
			   CV_INTER_LINEAR + CV_WARP_FILL_OUTLIERS,
			   cvScalarAll( 0 ) );
	cvNamedWindow( "Xformed", 1 );
	cvShowImage( "Xformed", xformed );
	cvWaitKey( 0 );
	cvReleaseImage( &xformed );
	cvReleaseMat( &H );
      }
  }
  */

  cvReleaseImage( &stacked );
  cvReleaseImage( &img1 );
  cvReleaseImage( &img2 );
  kdtree_release( kd_root );
  free( feat1 );
  free( feat2 );
  return 0;
}