sift.h File Reference

Functions for detecting SIFT image features. More...

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Detailed Description

Functions for detecting SIFT image features.

For more information, refer to:

Lowe, D. Distinctive image features from scale-invariant keypoints. International Journal of Computer Vision, 60, 2 (2004), pp.91--110.

Copyright (C) 2006 Rob Hess <hess@eecs.oregonstate.edu>

Note: The SIFT algorithm is patented in the United States and cannot be used in commercial products without a license from the University of British Columbia. For more information, refer to the file LICENSE.ubc that accompanied this distribution.

Version:

1.1.1-20070119

Definition in file sift.h.

Go to the source code of this file.

Classes
struct	detection_data
	holds feature data relevant to detection More...
Defines
#define	SIFT_INTVLS   3
	default number of sampled intervals per octave
#define	SIFT_SIGMA   1.6
	default sigma for initial gaussian smoothing
#define	SIFT_CONTR_THR   0.04
	default threshold on keypoint contrast |D(x)|
#define	SIFT_CURV_THR   10
	default threshold on keypoint ratio of principle curvatures
#define	SIFT_IMG_DBL   1
	double image size before pyramid construction?
#define	SIFT_DESCR_WIDTH   4
	default width of descriptor histogram array
#define	SIFT_DESCR_HIST_BINS   8
	default number of bins per histogram in descriptor array
#define	SIFT_INIT_SIGMA   0.5
#define	SIFT_IMG_BORDER   5
#define	SIFT_MAX_INTERP_STEPS   5
#define	SIFT_ORI_HIST_BINS   36
#define	SIFT_ORI_SIG_FCTR   1.5
#define	SIFT_ORI_RADIUS   3.0 * SIFT_ORI_SIG_FCTR
#define	SIFT_ORI_SMOOTH_PASSES   2
#define	SIFT_ORI_PEAK_RATIO   0.8
#define	SIFT_DESCR_SCL_FCTR   3.0
#define	SIFT_DESCR_MAG_THR   0.2
#define	SIFT_INT_DESCR_FCTR   512.0
#define	feat_detection_data(f)   ( (struct detection_data*)(f->feature_data) )
Functions
int	sift_features (IplImage *img, struct feature **feat)
	Finds SIFT features in an image using default parameter values.
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)
	Finda SIFT features in an image using user-specified parameter values.

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Function Documentation

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
	)

Finda SIFT features in an image using user-specified parameter values.

All detected features are stored in the array pointed to by feat.

Parameters:

img	the image in which to detect features
feat	a pointer to an array in which to store detected features
intvls	the number of intervals sampled per octave of scale space
sigma	the amount of Gaussian smoothing applied to each image level before building the scale space representation for an octave
contr_thr	a threshold on the value of the scale space function , where is a vector specifying feature location and scale, used to reject unstable features; assumes pixel values in the range [0, 1]
curv_thr	threshold on a feature's ratio of principle curvatures used to reject features that are too edge-like
img_dbl	should be 1 if image doubling prior to scale space construction is desired or 0 if not
descr_width	the width, , of the array of orientation histograms used to compute a feature's descriptor
descr_hist_bins	the number of orientations in each of the histograms in the array used to compute a feature's descriptor

Returns:

Returns the number of keypoints stored in feat or -1 on failure

See also:

sift_features()

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

Finds SIFT features in an image using default parameter values.

All detected features are stored in the array pointed to by feat.

Parameters:

img	the image in which to detect features
feat	a pointer to an array in which to store detected features

Returns:

Returns the number of features stored in feat or -1 on failure

See also:

_sift_features()