NAME
im_matinv, im_matmul, im_mattrn - matrix operations on DOUBLEMASKs
SYNOPSIS
#include <vips/vips.h>
DOUBLEMASK *im_matinv( const DOUBLEMASK *in, const char *name );
int im_matinv_inplace( DOUBLEMASK *mat );
DOUBLEMASK *im_matmul( in1, in2, name )
DOUBLEMASK *in1, *in2;
char *name;
DOUBLEMASK *im_matcat( in1, in2, name )
DOUBLEMASK *in1, *in2;
char *name;
DOUBLEMASK *im_mattrn( in, name )
DOUBLEMASK *in;
char *name;
DESCRIPTION
These functions treat DOUBLEMASKs as matricies, performing some of the
basics of matrix algebra on them.
There should be more matrix functions: those implemeneted are just
sufficient for the Gallery’s calibration routines. im_matadd,
im_matidentity should really be added.
None of these functions damage their arguments, except
im_matinv_inplace(3).
im_matinv(3) inverts DOUBLEMASK in, returning a new DOUBLEMASK, called
name, which contains the inverse of in. If no inverse exists, NULL is
returned and im_error(3) is called with a diagnostic message.
im_matinv_inplace(3) is as im_matinv(3) except that it overwrites its
input.
im_matmul() multiples the matrices held in in1 and in2, returning their
product in a matrix called name.
im_matcat() returns a new matrix formed by appending matrix in2 to the
end of matrix in1. The two matricies must be the same width. It is
useful for combining several im_measure()s into a single matrix.
im_mattrn() transposes matrix in, returning the transpose in new matrix
called name.
NOTES
DO NOT use matrix inversion to solve systems of linear equations
(SLEs). The routines im_lu_decomp(3) and im_lu_solve(3) are more
efficient, even for a single SLE.
RETURN VALUE
The functions returns a new DOUBLEMASK on sucess, and NULL on failure.
im_matinv_inplace(3) returns zero on success, and -1 on failure.
SEE ALSO
im_create_dmask(3), im_measure(3), etc. im_lu_decomp(3),
im_lu_solve(3)
COPYRIGHT
National Gallery, 1992. Tom Vajzovic, 2006
AUTHORS
J. Cupitt
Tom Vajzovic
2 May 1991 IM_MATINV(3)