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/* file: siftmatch.c
** author: Andrea Vedaldi
** description: SIFT descriptor matching.
**/
/* AUTORIGHTS
Copyright (c) 2006 The Regents of the University of California.
All Rights Reserved.
Created by Andrea Vedaldi
UCLA Vision Lab - Department of Computer Science
Permission to use, copy, modify, and distribute this software and its
documentation for educational, research and non-profit purposes,
without fee, and without a written agreement is hereby granted,
provided that the above copyright notice, this paragraph and the
following three paragraphs appear in all copies.
This software program and documentation are copyrighted by The Regents
of the University of California. The software program and
documentation are supplied "as is", without any accompanying services
from The Regents. The Regents does not warrant that the operation of
the program will be uninterrupted or error-free. The end-user
understands that the program was developed for research purposes and
is advised not to rely exclusively on the program for any reason.
This software embodies a method for which the following patent has
been issued: "Method and apparatus for identifying scale invariant
features in an image and use of same for locating an object in an
image," David G. Lowe, US Patent 6,711,293 (March 23,
2004). Provisional application filed March 8, 1999. Asignee: The
University of British Columbia.
IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND
ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. THE UNIVERSITY OF
CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS"
BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE
MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*/
#include"mexutils.c"
#include<stdlib.h>
#include<string.h>
#include<math.h>
#define greater(a,b) ((a) > (b))
#define min(a,b) (((a)<(b))?(a):(b))
#define max(a,b) (((a)>(b))?(a):(b))
#define TYPEOF_mxDOUBLE_CLASS double
#define TYPEOF_mxSINGLE_CLASS float
#define TYPEOF_mxINT8_CLASS char
#define TYPEOF_mxUINT8_CLASS unsigned char
#define PROMOTE_mxDOUBLE_CLASS double
#define PROMOTE_mxSINGLE_CLASS float
#define PROMOTE_mxINT8_CLASS int
#define PROMOTE_mxUINT8_CLASS int
#define MAXVAL_mxDOUBLE_CLASS mxGetInf()
#define MAXVAL_mxSINGLE_CLASS ((float)mxGetInf())
#define MAXVAL_mxINT8_CLASS 0x7fffffff
#define MAXVAL_mxUINT8_CLASS 0x7fffffff
typedef struct
{
int k1 ;
int k2 ;
double score ;
} Pair ;
/*
* This macro defines the matching function for abstract type; that
* is, it is a sort of C++ template. This is also a good illustration
* of why C++ is preferable for templates :-)
*/
#define _COMPARE_TEMPLATE(MXC) \
Pair* compare_##MXC (Pair* pairs_iterator, \
const TYPEOF_##MXC * L1_pt, \
const TYPEOF_##MXC * L2_pt, \
int K1, int K2, int ND, float thresh) \
{ \
int k1, k2 ; \
const PROMOTE_##MXC maxval = MAXVAL_##MXC ; \
for(k1 = 0 ; k1 < K1 ; ++k1, L1_pt += ND ) { \
\
PROMOTE_##MXC best = maxval ; \
PROMOTE_##MXC second_best = maxval ; \
int bestk = -1 ; \
\
/* For each point P2[k2] in the second image... */ \
for(k2 = 0 ; k2 < K2 ; ++k2, L2_pt += ND) { \
\
int bin ; \
PROMOTE_##MXC acc = 0 ; \
for(bin = 0 ; bin < ND ; ++bin) { \
PROMOTE_##MXC delta = \
((PROMOTE_##MXC) L1_pt[bin]) - \
((PROMOTE_##MXC) L2_pt[bin]) ; \
acc += delta*delta ; \
} \
\
/* Filter the best and second best matching point. */ \
if(acc < best) { \
second_best = best ; \
best = acc ; \
bestk = k2 ; \
} else if(acc < second_best) { \
second_best = acc ; \
} \
} \
\
L2_pt -= ND*K2 ; \
\
/* Lowe's method: accept the match only if unique. */ \
if(thresh * (float) best <= (float) second_best && \
bestk != -1) { \
pairs_iterator->k1 = k1 ; \
pairs_iterator->k2 = bestk ; \
pairs_iterator->score = best ; \
pairs_iterator++ ; \
} \
} \
\
return pairs_iterator ; \
} \
_COMPARE_TEMPLATE( mxDOUBLE_CLASS )
_COMPARE_TEMPLATE( mxSINGLE_CLASS )
_COMPARE_TEMPLATE( mxINT8_CLASS )
_COMPARE_TEMPLATE( mxUINT8_CLASS )
void
mexFunction(int nout, mxArray *out[],
int nin, const mxArray *in[])
{
int K1, K2, ND ;
void* L1_pt ;
void* L2_pt ;
double thresh = 1.5 ;
mxClassID data_class ;
enum {L1=0,L2,THRESH} ;
enum {MATCHES=0,D} ;
/* ------------------------------------------------------------------
** Check the arguments
** --------------------------------------------------------------- */
if (nin < 2) {
mexErrMsgTxt("At least two input arguments required");
} else if (nout > 2) {
mexErrMsgTxt("Too many output arguments");
}
if(!mxIsNumeric(in[L1]) ||
!mxIsNumeric(in[L2]) ||
mxGetNumberOfDimensions(in[L1]) > 2 ||
mxGetNumberOfDimensions(in[L2]) > 2) {
mexErrMsgTxt("L1 and L2 must be two dimensional numeric arrays") ;
}
K1 = mxGetN(in[L1]) ;
K2 = mxGetN(in[L2]) ;
ND = mxGetM(in[L1]) ;
if(mxGetM(in[L2]) != ND) {
mexErrMsgTxt("L1 and L2 must have the same number of rows") ;
}
data_class = mxGetClassID(in[L1]) ;
if(mxGetClassID(in[L2]) != data_class) {
mexErrMsgTxt("L1 and L2 must be of the same class") ;
}
L1_pt = mxGetData(in[L1]) ;
L2_pt = mxGetData(in[L2]) ;
if(nin == 3) {
if(!uIsRealScalar(in[THRESH])) {
mexErrMsgTxt("THRESH should be a real scalar") ;
}
thresh = *mxGetPr(in[THRESH]) ;
} else if(nin > 3) {
mexErrMsgTxt("At most three arguments are allowed") ;
}
/* ------------------------------------------------------------------
** Do the job
** --------------------------------------------------------------- */
{
Pair* pairs_begin = (Pair*) mxMalloc(sizeof(Pair) * (K1+K2)) ;
Pair* pairs_iterator = pairs_begin ;
#define _DISPATCH_COMPARE( MXC ) \
case MXC : \
pairs_iterator = compare_##MXC(pairs_iterator, \
(const TYPEOF_##MXC*) L1_pt, \
(const TYPEOF_##MXC*) L2_pt, \
K1,K2,ND,thresh) ; \
break ; \
switch (data_class) {
_DISPATCH_COMPARE( mxDOUBLE_CLASS ) ;
_DISPATCH_COMPARE( mxSINGLE_CLASS ) ;
_DISPATCH_COMPARE( mxINT8_CLASS ) ;
_DISPATCH_COMPARE( mxUINT8_CLASS ) ;
default :
mexErrMsgTxt("Unsupported numeric class") ;
break ;
}
/* ---------------------------------------------------------------
* Finalize
* ------------------------------------------------------------ */
{
Pair* pairs_end = pairs_iterator ;
double* M_pt ;
double* D_pt = NULL ;
out[MATCHES] = mxCreateDoubleMatrix
(2, pairs_end-pairs_begin, mxREAL) ;
M_pt = mxGetPr(out[MATCHES]) ;
if(nout > 1) {
out[D] = mxCreateDoubleMatrix(1,
pairs_end-pairs_begin,
mxREAL) ;
D_pt = mxGetPr(out[D]) ;
}
for(pairs_iterator = pairs_begin ;
pairs_iterator < pairs_end ;
++pairs_iterator) {
*M_pt++ = pairs_iterator->k1 + 1 ;
*M_pt++ = pairs_iterator->k2 + 1 ;
if(nout > 1) {
*D_pt++ = pairs_iterator->score ;
}
}
}
mxFree(pairs_begin) ;
}
}
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