libvips/libsrc/arithmetic/im_point_bilinear.c

128 lines
3.4 KiB
C

/* @(#) Find the value at (x,y) in given band of image.
* @(#) Use bilinear interpolation if x or y are non-integral.
* @(#)
* @(#) int im_maxpos_vec(
* @(#) IMAGE *im,
* @(#) double x,
* @(#) double y,
* @(#) int band,
* @(#) double *val
* @(#) );
* @(#)
*
* Copyright: 2006, The Nottingham Trent University
*
* Author: Tom Vajzovic
*
* Written on: 2006-09-26
*/
/*
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
*/
/** HEADERS **/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /* HAVE_CONFIG_H */
#include <vips/intl.h>
#include <vips/vips.h>
#include <vips/r_access.h>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC */
/** EXPORTED FUNCTION **/
int im_point_bilinear( IMAGE *im, double x, double y, int band, double *val ){
#define FUNCTION_NAME "im_point_bilinear"
double x_frac= x - (int) x;
double y_frac= y - (int) y;
Rect need= { x, y, ( x_frac ? 2 : 1 ), ( y_frac ? 2 : 1 ) };
REGION *reg;
if( im_pincheck( im ) )
return -1;
if( im-> Coding ){
im_error( FUNCTION_NAME, "%s", _("uncoded images only") );
return -1;
}
if( !( im_isint( im ) || im_isfloat( im ) ) ){
im_error( FUNCTION_NAME, "%s", _("scalar images only") );
return -1;
}
if( band >= im-> Bands || x < 0.0 || y < 0.0 || x > im-> Xsize || y > im-> Ysize ){
im_error( FUNCTION_NAME, "%s", _("coords outside image") );
return -1;
}
if( ! val ){
im_error( FUNCTION_NAME, "%s", _("invalid arguments") );
return -1;
}
reg= im_region_create( im );
if( ! reg || im_prepare( reg, &need ) )
return -1;
if( ! im_rect_includesrect( &reg-> valid, &need ) ){
im_error( FUNCTION_NAME, "%s", _("coords outside image") );
im_region_free( reg );
return -1;
}
if( x_frac )
if( y_frac )
*val= x_frac * y_frac * IM_REGION_VALUE( reg, ((int)x + 1), ((int)y + 1), band )
+ x_frac * ( 1.0 - y_frac ) * IM_REGION_VALUE( reg, ((int)x + 1), (int)y , band )
+ ( 1.0 - x_frac ) * y_frac * IM_REGION_VALUE( reg, (int)x, ((int)y + 1), band )
+ ( 1.0 - x_frac ) * ( 1.0 - y_frac ) * IM_REGION_VALUE( reg, (int)x, (int)y , band );
else
*val= x_frac * IM_REGION_VALUE( reg, ((int)x + 1), (int)y, band )
+ ( 1.0 - x_frac ) * IM_REGION_VALUE( reg, (int)x, (int)y, band );
else
if( y_frac )
*val= y_frac * IM_REGION_VALUE( reg, (int)x, ((int)y + 1), band )
+ ( 1.0 - y_frac ) * IM_REGION_VALUE( reg, (int)x, (int)y , band );
else
*val= IM_REGION_VALUE( reg, (int)x, (int)y, band );
im_region_free( reg );
return 0;
#undef FUNCTION_NAME
}