1IM_MULTIPLY(3)             Library Functions Manual             IM_MULTIPLY(3)
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NAME

6       im_cmulnorm, im_multiply - multiply two images
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SYNOPSIS

9       #include <vips/vips.h>
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11       int im_cmulnorm(in1, in2, out)
12       IMAGE *in1, *in2, *out;
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14       int im_multiply(in1, in2, out)
15       IMAGE *in1, *in2, *out;
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DESCRIPTION

19       These functions operate on two images held by image descriptors in1 and
20       in2 and write the result to the image descriptor out.  Input images in1
21       and  in2 should have the same channels and the same sizes; however they
22       can be of different types.  Only the history of  the  image  descriptor
23       pointed by in1 is copied to out.
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25       im_multiply(3)  applied to two integer images multiplies the two images
26       and writes the output as:
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28        in1    | uchar   char   ushort  short  uint  int
29        -------+-----------------------------------------
30        in2    |
31        uchar  | ushort  short  ushort  short  uint  int
32        char   | short   short  short   short  int   int
33        ushort | ushort  short  ushort  short  uint  int
34        short  | short   short  short   short  int   int
35        uint   | uint    int    uint    int    uint  int
36        int    | int     int    int     int    int   int
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38       If one or more of the images is a floating point type,  the  output  is
39       FMTFLOAT,  unless one or more of the inputs is FMTDOUBLE, in which case
40       the output is also FMTDOUBLE.
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42       If one or more of the images is a complex type, the output  is  FMTCOM‐
43       PLEX,  unless  one or more of the inputs is FMTDPCOMPLEX, in which case
44       the output is also FMTDPCOMPLEX.
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46       For complex input pels (x1,y1) and (x2,y2), im_multiply() writes (x1*x2
47       - y1*y2, x1*y2 + x2*y1).
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49       im_cmulnorm(3)  multiplies  two  complex  images. The complex output is
50       normalised to 1 by dividing both the real and  the  imaginary  part  of
51       each pel with the norm; for instance if the complex multiplication pro‐
52       duces (a,b) then the  output  written  by  this  function  is  (a/norm,
53       b/norm),  where norm=a*a+b*b.  Result is checked for norm=0.  The func‐
54       tion is useful for phase correlation.  Both inputs should be complex.
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56       Result is float complex if both inputs are float complex.  In any other
57       case the result is double complex.
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BUGS

61       None of the functions checks the result for over/underflow.
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RETURN VALUE

64       All functions return 0 on success and -1 on error.
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SEE ALSO

67       im_subtract(3), im_lintra(3), im_add(3).
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AUTHOR

70       N. Dessipris - 22/04/1991
71       J. Cupitt (im_multiply) - 22/04/1991
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75                                 24 April 1991                  IM_MULTIPLY(3)