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

6       im_maplut - map an image through a lookup table
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SYNOPSIS

9       #include <vips/vips.h>
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11       int im_maplut(in, out, lut)
12       IMAGE *in, *out, *lut;
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DESCRIPTION

16       im_maplut()  maps an image through another image, acting as a LUT (Look
17       Up Table).  The lut may have any type, and the output image will be  of
18       that type.
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20       The  input image must be an unsigned integer types, that is, it must be
21       one of FMTUCHAR, FMTUSHORT or FMTUINT.
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23       If the input is FMTUCHAR, then the LUT must have 256 elements, in other
24       words, lut->Xsize * lut->Ysize == 256.
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26       If  the input is FMTUSHORT or FMTUINT, then the lut may have any number
27       of elements, and input pels whose value is greater  than  lut->Xsize  *
28       lut->Ysize  are  mapped  with the last LUT element. The function counts
29       and prints the number of image elements which overflow in this way.
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31       As regards bands, there are three cases:
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33          - If LUT has one band, then the input may have any number of  bands,
34       and
35          each band will pass through the same LUT.
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37          -  If  LUT has the same number of bands as the input, then each band
38       of the
39          input will be LUTed separately.
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41          - If the input has one band, then the LUT may  have  any  number  of
42       bands, and
43          the output will have the same number of bands as the LUT.
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RETURN VALUE

47       All functions returns 0 on success and -1 on error.
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SEE ALSO

50       im_histgr(3), im_hsp(3), im_heq(3), im_identity(3).
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53       1995, National Gallery and Birkbeck College
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AUTHORS

56       J. Cupitt, 1995
57       N. Dessipris - 10/05/1991
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61                                  10 May 1991                     IM_MAPLUT(3)
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