NAME
im_cmulnorm, im_multiply - multiply two images
SYNOPSIS
#include <vips/vips.h>
int im_cmulnorm(in1, in2, out)
IMAGE *in1, *in2, *out;
int im_multiply(in1, in2, out)
IMAGE *in1, *in2, *out;
DESCRIPTION
These functions operate on two images held by image descriptors in1 and
in2 and write the result to the image descriptor out. Input images in1
and in2 should have the same channels and the same sizes; however they
can be of different types. Only the history of the image descriptor
pointed by in1 is copied to out.
im_multiply(3) applied to two integer images multiplies the two images
and writes the output as:
in1 | uchar char ushort short uint int
-------+-----------------------------------------
in2 |
uchar | ushort short ushort short uint int
char | short short short short int int
ushort | ushort short ushort short uint int
short | short short short short int int
uint | uint int uint int uint int
int | int int int int int int
If one or more of the images is a floating point type, the output is
FMTFLOAT, unless one or more of the inputs is FMTDOUBLE, in which case
the output is also FMTDOUBLE.
If one or more of the images is a complex type, the output is
FMTCOMPLEX, unless one or more of the inputs is FMTDPCOMPLEX, in which
case the output is also FMTDPCOMPLEX.
For complex input pels (x1,y1) and (x2,y2), im_multiply() writes (x1*x2
- y1*y2, x1*y2 + x2*y1).
im_cmulnorm(3) multiplies two complex images. The complex output is
normalised to 1 by dividing both the real and the imaginary part of
each pel with the norm; for instance if the complex multiplication
produces (a,b) then the output written by this function is (a/norm,
b/norm), where norm=a*a+b*b. Result is checked for norm=0. The
function is useful for phase correlation. Both inputs should be
complex.
Result is float complex if both inputs are float complex. In any other
case the result is double complex.
BUGS
None of the functions checks the result for over/underflow.
RETURN VALUE
All functions return 0 on success and -1 on error.
SEE ALSO
im_subtract(3), im_lintra(3), im_add(3).
AUTHOR
N. Dessipris - 22/04/1991
J. Cupitt (im_multiply) - 22/04/1991
24 April 1991 IM_MULTIPLY(3)