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

6       im_exp10tra,   im_exptra,   im_expntra,   im_expntra_vec,  im_log10tra,
7       im_logtra, im_powtra,  im_powtra_vec  -  logarithmic,  exponential  and
8       power transform of an image
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SYNOPSIS

11       #include <vips/vips.h>
12
13       int im_expntra(in, out, base)
14       IMAGE *in, *out;
15       double base;
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17       int im_expntra_vec(in, out, n, vec)
18       IMAGE *in, *out;
19       int n;
20       double *vec;
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22       int im_exp10tra(in, out)
23       IMAGE *in, *out;
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25       int im_exptra(in, out)
26       IMAGE *in, *out;
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28       int im_log10tra(in, out)
29       IMAGE *in, *out;
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31       int im_logtra(in, out)
32       IMAGE *in, *out;
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34       int im_powtra(in, out, exponent)
35       IMAGE *in, *out;
36       double exponent;
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38       int im_powtra_vec(in, out, n, vec)
39       IMAGE *in, *out;
40       int n;
41       double *vec;
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DESCRIPTION

45       Each  of the above functions maps in through a log or anti-log function
46       of some sort and writes the result to out. The size and number of bands
47       are unchanged, the output type is float, unless the input is double, in
48       which case the output is double. Non-complex images only!
49
50       im_expntra(3) transforms element x of input, to pow(base, x) in output.
51       It  detects  division by zero, setting those pixels to zero in the out‐
52       put. Beware: it does this silently!
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54       im_expntra_vec(3) works as im_expntra(), but lets you  specify  a  con‐
55       stant per band.
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57       im_exp10tra(3)  transforms  element x of input, to pow(10,0, x) in out‐
58       put. Internally, it is defined in terms of im_expntra().
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60       im_exptra(3) transforms element x of input, to  pow(e,  x)  in  output,
61       where  e  is  the  mathematical  constant. Internally, it is defined in
62       terms of im_expntra().
63
64       im_log10tra(3) transforms element x of input, to log10tra(x) in output.
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66       im_logtra(3) transforms element x of input, to logtra(x) in output.
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68       im_powtra(3) transforms element x of input, to pow(x, exponent) in out‐
69       put.  It  detects division by zero, setting those pixels to zero in the
70       output. Beware: it does this silently!
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72       im_powtra_vec(3) works as im_powtra(3), but lets you specify a constant
73       per band.
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BUGS

77       None  of the functions checks for under/overflow. Overflow is very com‐
78       mon for many of these functions!
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RETURN VALUE

82       Each function returns 0 on success and -1 on error.
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SEE ALSO

85       im_add(3), im_multiply(3), im_subtract(3),  im_lintra(3),  im_absim(3),
86       im_mean(3), im_max(3).
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AUTHOR

89       N. Dessipris - 24/04/1991
90       J. Cupitt (rewrite) - 21/7/93
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94                                 24 April 1991                    IM_EXPTRA(3)
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