/* Call im_spcor via arg vector.
*/
static int
spcor_vec( im_object *argv )
{
return( im_spcor( argv[0], argv[1], argv[2] ) );
}
/**
* im_correl:
* @ref: reference image
* @sec: secondary image
* @xref: position in reference image
* @yref: position in reference image
* @xsec: position in secondary image
* @ysec: position in secondary image
* @hwindowsize: half window size
* @hsearchsize: half search size
* @correlation: return detected correlation
* @x: return found position
* @y: return found position
*
* This operation finds the position of @sec within @ref.
*
* The area around
* (@xsec, @ysec) is searched for the best match to the area around (@xref,
* @yref). It searches an area of size @hsearchsize for a
* match of size @hwindowsize. The position of the best match is
* returned, together with the correlation at that point.
*
* Only the first band of each image is correlated. @ref and @sec may be
* very large --- the function extracts and generates just the
* parts needed. Correlation is done with im_spcor(); the position of
* the maximum is found with im_maxpos().
*
* See also: im_match_linear(), im_match_linear_search(), im_lrmosaic().
*
* Returns: 0 on success, -1 on error
*/
int
im_correl( IMAGE *ref, IMAGE *sec,
int xref, int yref, int xsec, int ysec,
int hwindowsize, int hsearchsize,
double *correlation, int *x, int *y )
{
IMAGE *surface = im_open( "surface", "t" );
IMAGE *t1, *t2, *t3, *t4;
Rect refr, secr;
Rect winr, srhr;
Rect wincr, srhcr;
if( !surface ||
!(t1 = im_open_local( surface, "correlate:1", "p" )) ||
!(t2 = im_open_local( surface, "correlate:1", "p" )) ||
!(t3 = im_open_local( surface, "correlate:1", "p" )) ||
!(t4 = im_open_local( surface, "correlate:1", "p" )) )
return( -1 );
/* Find position of window and search area, and clip against image
* size.
*/
refr.left = 0;
refr.top = 0;
refr.width = ref->Xsize;
refr.height = ref->Ysize;
winr.left = xref - hwindowsize;
winr.top = yref - hwindowsize;
winr.width = hwindowsize*2 + 1;
winr.height = hwindowsize*2 + 1;
im_rect_intersectrect( &refr, &winr, &wincr );
secr.left = 0;
secr.top = 0;
secr.width = sec->Xsize;
secr.height = sec->Ysize;
srhr.left = xsec - hsearchsize;
srhr.top = ysec - hsearchsize;
srhr.width = hsearchsize*2 + 1;
srhr.height = hsearchsize*2 + 1;
im_rect_intersectrect( &secr, &srhr, &srhcr );
/* Extract window and search area.
*/
if( im_extract_area( ref, t1,
wincr.left, wincr.top, wincr.width, wincr.height ) ||
im_extract_area( sec, t2,
srhcr.left, srhcr.top, srhcr.width, srhcr.height ) ) {
im_close( surface );
return( -1 );
}
/* Make sure we have just one band. From im_*mosaic() we will, but
* from im_match_linear_search() etc. we may not.
*/
if( t1->Bands != 1 ) {
if( im_extract_band( t1, t3, 0 ) ) {
im_close( surface );
return( -1 );
}
t1 = t3;
}
if( t2->Bands != 1 ) {
if( im_extract_band( t2, t4, 0 ) ) {
im_close( surface );
return( -1 );
}
t2 = t4;
}
/* Search!
*/
if( im_spcor( t2, t1, surface ) ) {
im_close( surface );
return( -1 );
}
/* Find maximum of correlation surface.
*/
if( im_maxpos( surface, x, y, correlation ) ) {
im_close( surface );
return( -1 );
}
im_close( surface );
/* Translate back to position within sec.
*/
*x += srhcr.left;
*y += srhcr.top;
return( 0 );
}
