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