sift.h

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#ifndef SIFT_H
#define SIFT_H

#include <cxcore.h> // opencv

/******************************** Structures *********************************/

struct detection_data
{
  int r;
  int c;
  int octv;
  int intvl;
  double subintvl;
  double scl_octv;
};

struct feature;


/******************************* Defs and macros *****************************/

#define SIFT_INTVLS 3

#define SIFT_SIGMA 1.6

#define SIFT_CONTR_THR 0.04

#define SIFT_CURV_THR 10

#define SIFT_IMG_DBL 1

#define SIFT_DESCR_WIDTH 4

#define SIFT_DESCR_HIST_BINS 8

/* assumed gaussian blur for input image */
#define SIFT_INIT_SIGMA 0.5

/* width of border in which to ignore keypoints */
#define SIFT_IMG_BORDER 5

/* maximum steps of keypoint interpolation before failure */
#define SIFT_MAX_INTERP_STEPS 5

/* default number of bins in histogram for orientation assignment */
#define SIFT_ORI_HIST_BINS 36

/* determines gaussian sigma for orientation assignment */
#define SIFT_ORI_SIG_FCTR 1.5

/* determines the radius of the region used in orientation assignment */
#define SIFT_ORI_RADIUS 3.0 * SIFT_ORI_SIG_FCTR

/* number of passes of orientation histogram smoothing */
#define SIFT_ORI_SMOOTH_PASSES 2

/* orientation magnitude relative to max that results in new feature */
#define SIFT_ORI_PEAK_RATIO 0.8

/* determines the size of a single descriptor orientation histogram */
#define SIFT_DESCR_SCL_FCTR 3.0

/* threshold on magnitude of elements of descriptor vector */
#define SIFT_DESCR_MAG_THR 0.2

/* factor used to convert floating-point descriptor to unsigned char */
#define SIFT_INT_DESCR_FCTR 512.0

/* returns a feature's detection data */
#define feat_detection_data(f) ( (struct detection_data*)(f->feature_data) )


/*************************** Function Prototypes *****************************/

extern int sift_features( IplImage* img, struct feature** feat );



extern int _sift_features( IplImage* img, struct feature** feat, int intvls,
         double sigma, double contr_thr, int curv_thr,
         int img_dbl, int descr_width, int descr_hist_bins );

#endif