NAME
im_measure - measure colour patches off images
SYNOPSIS
#include <vips/vips.h>
DOUBLEMASK *im_measure(in, box, h, v, sel, nsel, name)
IMAGE *in;
IMAGE_BOX *box;
int h, v;
int *sel;
int nsel;
char *name;
DESCRIPTION
Analyse a grid of colour patches, producing a DOUBLEMASK of averages.
Pass an IMAGE, an IMAGE_BOX, the number of horizontal and vertical
patches, an array giving the numbers of the patches to measure (patches
are numbered left-to-right, top-to-bottom, starting with 1) and the
name we should give the output mask. Return a DOUBLEMASK in which rows
are patches and columns are bands. Only the central 50% of each patch
is averaged.
Example: 6 band image of 4x2 block of colour patches.
+---+---+---+---+
| 1 | 2 | 3 | 4 |
+---+---+---+---+
| 5 | 6 | 7 | 8 |
+---+---+---+---+
Then call im_measure( im, box, 4, 2, { 2, 4 }, 2, "fred" ) makes a mask
"fred" which has 6 columns, two rows. The first row contains the
averages for patch 2, the second for patch 4.
Output warnings: a warning is issued if the standard deviation of any
patch is greater than 20% of the mean of that patch.
RETURN VALUE
NULL on error.
SEE ALSO
im_avg(3), im_deviate(3), im_stats(3).
24 October 1992