2007-08-29 18:23:50 +02:00
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.TH IM_RANK 3 "19 Aug 1996"
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.SH NAME
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im_rank, im_rank_raw \- rank filter
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.SH SYNOPSIS
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#include <vips/vips.h>
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int im_rank(in, out, xsize, ysize, n)
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.br
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IMAGE *in, *out;
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.br
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int xsize, ysize, n;
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int im_rank_raw(in, out, xsize, ysize, n)
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.br
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IMAGE *in, *out;
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.br
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int xsize, ysize, n;
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.SH DESCRIPTION
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.B im_rank()
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does rank filtering on an image. A window of size xsize by ysize
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is passed over the image. At each position, the pixels inside the window are
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sorted into ascending order and the pixel at the nth position is output. n
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numbers from 0.
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2009-03-28 18:07:55 +01:00
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It works for any non-complex image type, with any number of bands.
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The input
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is expanded by copying edge pixels before performing the operation so that the
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output image has the same size as the input. Edge pixels in the output image
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are therefore only approximate.
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2007-08-29 18:23:50 +02:00
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.B im_rank_raw()
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2009-03-28 18:07:55 +01:00
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works just as im_rank(), but does not expand the input.
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2007-08-29 18:23:50 +02:00
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.SH EXAMPLES
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For a median filter with mask size m (3 for 3x3, 5 for 5x5, etc.) use
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im_rank( in, out, m, m, m * m / 2 );
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The special cases n == 0 and n == m * m - 1 are useful dilate and expand
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operators.
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.SH RETURN VALUE
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The function returns 0 on success and -1 on error.
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.SH SEE ALSO
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im_conv(3), im_fastcor(3).
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.SH COPYRIGHT
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1989-1996 The National Gallery and Birkbeck College
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