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