ldxcorr(3)

LIBRARY ROUTINE
ldxcorr - determines a cross-correlation estimate between two input data sequences.

LIBRARY CALL
#include "vinclude.h"
int
ldxcorr ( image1, image2, arith_type, out_option, xpoints, process_dir )
int out_option, arith_type, xpoints, process_dir;
struct xvimage *image1, *image2;

INPUT

image1 (struct xvimage) - pointer to the input/output xvimage structure.
image2 (struct xvimage) - pointer to the input/output xvimage structure.
arith_type - 0 = scalar, 1 = complex.
out_option - 0 = biased, 1 = unbiased, 2 = FFT based.
points - length of cross-correlation estimate.
process_dir (int) - data processing direction. 0 = vector, 1 = band.

OUTPUT

image (struct xvimage) - pointer to the input/output xvimage structure.

MODIFICATIONS

Jeremy Worley 24 Feb 1992 23:15 MST
    changed call to lfft1d in ldfxcorr() to fft842_() since lfft1d is being phased out. Also cleaned up some implicitly defined functions and modularized ldfxcorr() which resulted in the creation of a static function called _lfxcorr(). Also fixed a small scaling problem with the output of ldfxcorr().

Jeremy Worley 05 Mar 1992 12:05 MST
    Fixed a call to fprintf() that was missing format specifiers. Added explicit declarations of ldfxcorr() and ldtxcorr().

DESCRIPTION

1D Cross-Correlation Estimate. Generates either the biased, unbiased or FFT based cross-correlation estimate of two data sequences. It can operate on Real and Complex data. If complex data, the user has the option of using complex arithmetic (vector) or real arithmetic (scalar = treat the real number and imaginary number independently). NOTE: complex data is expected to be in rectangular (not polar) form.
      Both sequences must be of the same data type.
      The cross-correlation function is not a symmetric function.

The number of cross-correlation points may be selected by the user. This number represents the number of points to the right of, and including the center point. The actual number of data points will be 2*s - 1, where s is the number of points to the right of, and including the center point.

dxcorr does not work on explicit location data and will return an error when such a file is encountered. No output file will be created. dxcorr works only on VFF_TYP_FLOAT or VFF_TYP_COMPLEX data files.

Input/Output Files

The input files must be of type VFF_TYP_FLOAT or VFF_TYP_COMPLEX. The output file returned will be of size specified by the user. *********************************************************************

The cross-correlation default option is the -g (biased estimate = 0) option. When this option is selected, dxcorr calculates the biased cross-correlation estimate.

Process direction

Data can be processed with either band or vector orientation (-d option). The default data processing direction is in the vector direction (-d = 0). This means that data stored in multiband format will be processed as a set pixel location. The direction of processing can be changed so that each band is processed as a signal (instead of each vector being a signal) by setting the -d option to 1.

SEE ALSO
dxcorr(1), intro(3), vipl(3), verror(3), vutils(3)

RESTRICTIONS

ldxcorr works only on VFF_TYP_FLOAT or VFF_TYP_COMPLEX data files.

AUTHOR
Ramiro Jordan, Jeremy Worley

COPYRIGHT
Copyright 1992, University of New Mexico. All rights reserved.