im_fastcor(3) im_fastcor(3)
NAME
im_fastcor, im_spcor - correlate two images
SYNOPSIS
#include <vips/vips.h>
int im_fastcor(in, ref, out)
IMAGE *in, *ref, *out;
int im_spcor(in, ref, out)
IMAGE *in, *ref, *out;
DESCRIPTION
These functions calculate spatial correlation between two one-band
images held by the image descriptors in and ref. The sizes of ref
should be smaller than the sizes of in. The correlation is carried out
by overlapping ref on the top left corner of in and moving it over in.
The output image is the same size as the input. The edge pixels are
calculated by expanding the input image using im_embed(3) in mode 1
(replicating edge pixels) just enough so that the output can match the
input.
im_spcor(3) calculates the spatial correlation between in and ref using
the correlation coefficient from Niblack "An Introduction to Digital
Image Processing,", Prentice/Hall, pp 138. The resultant coefficients
are written as float numbers in out. The images must be char, short or
ushort.
im_fastcor(3) simply returns the sum of squares of differences between
in and ref. This is much faster, but less useful. The resultant coef-
ficients are written as unsigned int numbers in out which has a size of
in.
BUGS
The functions do not check for integer overflow.
RETURN VALUE
The function returns 0 on success and -1 on error.
SEE ALSO
im_conv(3), im_lrmosaic(3).
COPYRIGHT
The National Gallery and Birkbeck College, 1990-1997.
14 May 1991 im_fastcor(3)
im_fastcor 7.14.5 - Generated Sun Sep 7 09:18:05 CDT 2008