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

6       im_measure - measure colour patches off images
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SYNOPSIS

9       #include <vips/vips.h>
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11       DOUBLEMASK *im_measure(in, box, h, v, sel, nsel, name)
12       IMAGE *in;
13       IMAGE_BOX *box;
14       int h, v;
15       int *sel;
16       int nsel;
17       char *name;
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DESCRIPTION

21       Analyse  a  grid of colour patches, producing a DOUBLEMASK of averages.
22       Pass an IMAGE, an IMAGE_BOX, the  number  of  horizontal  and  vertical
23       patches, an array giving the numbers of the patches to measure (patches
24       are numbered left-to-right, top-to-bottom, starting  with  1)  and  the
25       name  we should give the output mask. Return a DOUBLEMASK in which rows
26       are patches and columns are bands. Only the central 50% of  each  patch
27       is averaged.
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29       Example: 6 band image of 4x2 block of colour patches.
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31        +---+---+---+---+
32        | 1 | 2 | 3 | 4 |
33        +---+---+---+---+
34        | 5 | 6 | 7 | 8 |
35        +---+---+---+---+
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37       Then call im_measure( im, box, 4, 2, { 2, 4 }, 2, "fred" ) makes a mask
38       "fred" which has 6 columns, two rows. The first row contains the  aver‐
39       ages for patch 2, the second for patch 4.
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41       Output  warnings:  a warning is issued if the standard deviation of any
42       patch is greater than 20% of the mean of that patch.
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RETURN VALUE

46       NULL on error.
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SEE ALSO

49       im_avg(3), im_deviate(3), im_stats(3).
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53                                24 October 1992                  IM_MEASURE(3)
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