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 coefficients 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.