158 lines
6.0 KiB
C
158 lines
6.0 KiB
C
/* This function implements:
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* "Extension of Phase Correlation to Subpixel Registration"
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* by H. Foroosh, from IEEE trans. Im. Proc. 11(3), 2002.
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*
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* If the best three matches in the correlation are aranged:
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*
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* 02 or 01
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* 1 2
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*
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* then we return a subpixel match using the ratio of correlations in the
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* vertical and horizontal dimension.
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*
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* ( xs[0], ys[0] ) is the best integer alignment
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* ( xs[ use_x ], ys[ use_x ] ) is equal in y and (+/-)1 off in x
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* ( xs[ use_y ], ys[ use_y ] ) is equal in x and (+/-)1 off in y
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*
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*
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* Alternatively if the best four matches in the correlation are aranged in
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* a square:
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*
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* 01 or 03 or 02 or 03
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* 32 12 31 21
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*
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* then we return a subpixel match weighting with the sum the two on each
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* side over the sum of all four, but only if all four of them are very
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* close to the best, and the fifth is nowhere near.
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*
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* This alternative method is not described by Foroosh, but is often the
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* case where the match is close to n-and-a-half pixels in both dimensions.
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*
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* Copyright: 2008, Nottingham Trent University
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*
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* Author: Tom Vajzovic
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*
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* Written on: 2008-02-07
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*/
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/*
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This file is part of VIPS.
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VIPS is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/*
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These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif /*HAVE_CONFIG_H */
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#include <vips/intl.h>
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#include <stdlib.h>
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#include <vips/vips.h>
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#ifdef WITH_DMALLOC
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#include <dmalloc.h>
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#endif /*WITH_DMALLOC */
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#define MOST_OF( A, B ) ( (A) > 0.9 * (B) )
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#define LITTLE_OF( A, B ) ( (B) < 0.1 * (B) )
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int im_maxpos_subpel( IMAGE *in, double *x, double *y ){
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#define FUNCTION_NAME "im_maxpos_subpel"
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int xs[5];
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int ys[5];
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double vals[5];
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int xa, ya, xb, yb;
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double vxa, vya, vxb, vyb;
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if( im_maxpos_vec( in, xs, ys, vals, 5 ))
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return -1;
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#define WRAP_TEST_RETURN() \
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\
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/* wrap around if we have alignment -1 < d <= 0 */ \
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/* (change it to: size - 1 <= d < size ) */ \
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\
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if( ! xa && in-> Xsize - 1 == xb ) \
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xa= in-> Xsize; \
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\
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else if( ! xb && in-> Xsize - 1 == xa ) \
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xb= in-> Xsize; \
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\
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if( ! ya && in-> Ysize - 1 == yb ) \
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ya= in-> Ysize; \
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\
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else if( ! yb && in-> Ysize - 1 == ya ) \
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yb= in-> Ysize; \
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\
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if( 1 == abs( xb - xa ) && 1 == abs( yb - ya )){ \
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*x= ((double)xa) + ((double)( xb - xa )) * ( vxb / ( vxa + vxb )); \
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*y= ((double)ya) + ((double)( yb - ya )) * ( vyb / ( vya + vyb )); \
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return 0; \
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}
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#define TEST3( A, B ) \
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if( xs[0] == xs[A] && ys[0] == ys[B] ){ \
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xa= xs[0]; \
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ya= ys[0]; \
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xb= xs[B]; \
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yb= ys[A]; \
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vxa= vals[0]; \
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vya= vals[0]; \
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vxb= vals[B]; \
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vyb= vals[A]; \
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WRAP_TEST_RETURN() \
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}
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TEST3( 1, 2 )
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TEST3( 2, 1 )
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if( MOST_OF( vals[1], vals[0] ) && MOST_OF( vals[2], vals[0] )
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&& MOST_OF( vals[3], vals[0] ) && LITTLE_OF( vals[4], vals[0] )){
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#define TEST4( A, B, C, D, E, F, G, H ) \
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if( xs[A] == xs[B] && xs[C] == xs[D] && ys[E] == ys[F] && ys[G] == ys[H] ){ \
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xa= xs[A]; \
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xb= xs[C]; \
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ya= ys[E]; \
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yb= ys[G]; \
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vxa= vals[A] + vals[B]; \
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vxb= vals[C] + vals[D]; \
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vya= vals[E] + vals[F]; \
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vyb= vals[G] + vals[H]; \
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WRAP_TEST_RETURN() \
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}
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TEST4( 0, 3, 1, 2, 0, 1, 2, 3 )
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TEST4( 0, 1, 2, 3, 0, 3, 1, 2 )
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TEST4( 0, 3, 1, 2, 0, 2, 1, 3 )
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TEST4( 0, 2, 1, 3, 0, 3, 1, 2 )
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}
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im_warn( FUNCTION_NAME, "registration performed to nearest pixel only: correlation does not have the expected distribution for sub-pixel registration" );
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*x= (double) xs[0];
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*y= (double) ys[0];
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return 0;
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}
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