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im_rank(3)                                                          im_rank(3)




NAME

       im_rank, im_rank_raw - rank filter


SYNOPSIS

       #include <vips/vips.h>

       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 posi-
       tion 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 opera-
       tion so that the output image has the same size as the input. Edge pix-
       els 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.


SEE ALSO

       im_conv(3), im_fastcor(3).


COPYRIGHT

       1989-1996 The National Gallery and Birkbeck College



                                  19 Aug 1996                       im_rank(3)

vips 7.18.1 - Generated Sat Apr 18 09:45:03 CDT 2009
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