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NAME

       im_correl - search for image match

SYNOPSIS

       #include <vips/vips.h>

       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 )

DESCRIPTION

       im_correl()  is the base image-searching function used by the mosaicing
       functions im_lrmosaic() and im_tbmosaic(), and by the matching funtions
       im_match_linear() and im_match_linear_search().

       It  finds  the  position  of  the  secondary  image sec within ref.  It
       searches the area around xsec , ysec for the best match  for  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  generated  just  the  parts
       needed.  Correlation  is  done  with  im_spcor();  the  position of the
       maximum is found with im_maxpos().

SEE ALSO

       im_fastcor(3),    im_spcor(3),    im_maxpos(3),     im_match_linear(3),
       im_lrmosaic(3).

AUTHOR

       J.Cupitt - 22/02/93

COPYRIGHT

       The National Gallery and Birkbeck College, 1989-1996.

                                  13 May 1991