examples/OpenCV/siftDetector/hess/xform.h File Reference#include <cxcore.h>
Go to the source code of this file.
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Classes |
struct | ransac_data |
Defines |
#define | RANSAC_ERR_TOL 3 |
#define | RANSAC_INLIER_FRAC_EST 0.25 |
#define | RANSAC_PROB_BAD_SUPP 0.10 |
#define | feat_ransac_data(feat) ( (struct ransac_data*) (feat)->feature_data ) |
Typedefs |
typedef CvMat *(* | ransac_xform_fn )(CvPoint2D64f *pts, CvPoint2D64f *mpts, int n) |
typedef double(* | ransac_err_fn )(CvPoint2D64f pt, CvPoint2D64f mpt, CvMat *T) |
Functions |
CvMat * | ransac_xform (struct feature *features, int n, int mtype, ransac_xform_fn xform_fn, int m, double p_badxform, ransac_err_fn err_fn, double err_tol, struct feature ***inliers, int *n_in) |
CvMat * | lsq_homog (CvPoint2D64f *pts, CvPoint2D64f *mpts, int n) |
double | homog_xfer_err (CvPoint2D64f pt, CvPoint2D64f mpt, CvMat *H) |
CvPoint2D64f | persp_xform_pt (CvPoint2D64f pt, CvMat *T) |
Detailed Description
Functions for computing transforms from image feature correspondences.
Copyright (C) 2006-2007 Rob Hess <hess@eecs.oregonstate.edu>
- Version:
- 1.1.1-20070913
Definition in file xform.h.
Define Documentation
#define RANSAC_INLIER_FRAC_EST 0.25 |
pessimistic estimate of fraction of inlers for RANSAC
Definition at line 32 of file xform.h.
Referenced by ransac_xform().
#define RANSAC_PROB_BAD_SUPP 0.10 |
estimate of the probability that a correspondence supports a bad model
Definition at line 35 of file xform.h.
Referenced by ransac_xform().
Typedef Documentation
typedef double(* ransac_err_fn)(CvPoint2D64f pt, CvPoint2D64f mpt, CvMat *T) |
Prototype for error functions passed to ransac_xform(). For a given point, its correspondence, and a transform, functions of this type should compute a measure of error between the correspondence and the point after the point has been transformed by the transform.
- Parameters:
-
| pt | a point |
| mpt | pt's correspondence |
| T | a transform |
- Returns:
- Should return a measure of error between mpt and pt after pt has been transformed by the transform T.
Definition at line 71 of file xform.h.
typedef CvMat*(* ransac_xform_fn)(CvPoint2D64f *pts, CvPoint2D64f *mpts, int n) |
Prototype for transformation functions passed to ransac_xform(). Functions of this type should compute a transformation matrix given a set of point correspondences.
- Parameters:
-
| pts | array of points |
| mpts | array of corresponding points; each pts[i], i=0..n-1, corresponds to mpts[i] |
| n | number of points in both pts and mpts |
- Returns:
- Should return a transformation matrix that transforms each point in pts to the corresponding point in mpts or NULL on failure.
Definition at line 54 of file xform.h.
Function Documentation
double homog_xfer_err |
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CvPoint2D64f |
pt, |
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CvPoint2D64f |
mpt, |
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CvMat * |
H | |
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Calculates the transfer error between a point and its correspondence for a given homography, i.e. for a point , it's correspondence , and homography , computes . Intended for use as a ransac_err_fn.
- Parameters:
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| pt | a point |
| mpt | pt's correspondence |
| H | a homography matrix |
- Returns:
- Returns the transfer error between pt and mpt given H
Definition at line 239 of file xform.cpp.
CvMat* lsq_homog |
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CvPoint2D64f * |
pts, |
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CvPoint2D64f * |
mpts, |
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int |
n | |
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Calculates a least-squares planar homography from point correspondeces. Intended for use as a ransac_xform_fn.
- Parameters:
-
| pts | array of points |
| mpts | array of corresponding points; each pts[i], i=0..n-1, corresponds to mpts[i] |
| n | number of points in both pts and mpts; must be at least 4 |
- Returns:
- Returns the
least-squares planar homography matrix that transforms points in pts to their corresponding points in mpts or NULL if fewer than 4 correspondences were provided
Definition at line 182 of file xform.cpp.
CvPoint2D64f persp_xform_pt |
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CvPoint2D64f |
pt, |
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CvMat * |
T | |
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Performs a perspective transformation on a single point. That is, for a point and a matrix this function returns the point , where
,
and
.
Note that affine transforms are a subset of perspective transforms.
- Parameters:
-
| pt | a 2D point |
| T | a perspective transformation matrix |
- Returns:
- Returns the point
as above.
Definition at line 266 of file xform.cpp.
Calculates a best-fit image transform from image feature correspondences using RANSAC.
For more information refer to:
Fischler, M. A. and Bolles, R. C. Random sample consensus: a paradigm for model fitting with applications to image analysis and automated cartography. Communications of the ACM, 24, 6 (1981), pp. 381--395.
- Parameters:
-
| features | an array of features; only features with a non-NULL match of type mtype are used in homography computation |
| n | number of features in feat |
| mtype | determines which of each feature's match fields to use for transform computation; should be one of FEATURE_FWD_MATCH, FEATURE_BCK_MATCH, or FEATURE_MDL_MATCH; if this is FEATURE_MDL_MATCH, correspondences are assumed to be between a feature's img_pt field and its match's mdl_pt field, otherwise correspondences are assumed to be between the the feature's img_pt field and its match's img_pt field |
| xform_fn | pointer to the function used to compute the desired transformation from feature correspondences |
| m | minimum number of correspondences necessary to instantiate the transform computed by xform_fn |
| p_badxform | desired probability that the final transformation returned by RANSAC is corrupted by outliers (i.e. the probability that no samples of all inliers were drawn) |
| err_fn | pointer to the function used to compute a measure of error between putative correspondences and for a given transform |
| err_tol | correspondences within this distance of each other are considered as inliers for a given transform |
| inliers | if not NULL, output as an array of pointers to the final set of inliers |
| n_in | if not NULL, output as the final number of inliers |
- Returns:
- Returns a transformation matrix computed using RANSAC or NULL on error or if an acceptable transform could not be computed.
Definition at line 76 of file xform.cpp.
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