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

6       im_extract, im_extract_band, im_extract_bands, im_etract_area - extract
7       a portion of an image
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SYNOPSIS

10       #include <vips/vips.h>
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12       int im_extract(in, out, pbox)
13       IMAGE *in, *out;
14       IMAGE_BOX *pbox;
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16       int im_extract_band(in, out, band)
17       IMAGE *in, *out;
18       int band;
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20       int im_extract_bands(in, out, band, nbands)
21       IMAGE *in, *out;
22       int band;
23       int nbands;
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25       int im_extract_area(in, out, x, y, w, h)
26       IMAGE *in, *out;
27       int x, y, w, h;
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DESCRIPTION

31       im_extract(3) extracts a portion of the image pointed by in and  writes
32       the  result to out. pbox specifies the size and position of the area to
33       be extracted and is defined as
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35         /* Used to define a region of interest for
36          * im_extract() etc.
37          */
38         typedef struct {
39           int xstart;
40           int ystart;
41           int xsize;
42           int ysize;
43           int chsel;
44         } IMAGE_BOX;
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46       see  <vips/vips.h>.  if  pbox->chsel  is  set  to  -1,  all  bands  are
47       extracted;  otherwise  pbox->chsel gives the band to extract, numbering
48       from zero. The area specified by pbox  must  lie  entirely  within  the
49       image.
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51       Works for any size image, any number of bands, any type. Works for LAB‐
52       PACK coded images too! But disallows band extraction in this case.
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54       If used as part of a pipeline of partial image operations, im_extract()
55       magically vanishes if chsel is -1. See the VIPS IO System Guide.
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57       im_extract_area(3)  is  a  convenience  function which extracts an area
58       from an image, leaving the bands the same.
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60       im_extract_bands(3) takes nbands out of an image,  starting  from  band
61       band.   So,  for  example, nbands == 2, bands == 1 will form a two band
62       image from an RGB image, where the two bands are the G and the B bands.
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64       im_extract_band(3) is a convenience function which  extracts  a  single
65       band from an image.
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RETURN VALUE

69       The function returns 0 on success and -1 on error.
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SEE ALSO

72       im_insert(3),       im_lrjoin(3),      im_lrmerge(3),      im_stats(3),
73       im_region_region(3).
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76       J. Cupitt,
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AUTHOR

79       J. Cupitt - 11/04/1990
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83                                 11 April 1990                   IM_EXTRACT(3)
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