int im_rank(in, out, xsize, ysize, n)
IMAGE *in, *out;
int xsize, ysize, n;

int im_rank_raw(in, out, xsize, ysize, n)
IMAGE *in, *out;
int xsize, ysize, n;

DESCRIPTION

im_rank()
does rank filtering on an image. A window of size xsize by ysize
is passed over the image. At each position, the pixels inside the window are
sorted into ascending order and the pixel at the nth position is output. n
numbers from 0.

It works for any non-complex image type, with any number of bands.
The input
is expanded by copying edge pixels before performing the operation so that the
output image has the same size as the input. Edge pixels in the output image
are therefore only approximate.

im_rank_raw()
works just as im_rank(), but does not expand the input.

EXAMPLES

For a median filter with mask size m (3 for 3x3, 5 for 5x5, etc.) use

im_rank( in, out, m, m, m * m / 2 );

The special cases n == 0 and n == m * m - 1 are useful dilate and expand
operators.

RETURN VALUE

The function returns 0 on success and -1 on error.