pgmmedian(1)

1Pgmmedian User Manual(0)                              Pgmmedian User Manual(0)
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NAME

6       pgmmedian - apply a median filter to a PGM file
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SYNOPSIS

10       pgmmedian
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12       [-width=n]
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14       [-height=n]
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16       [-type=median_type]
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18       [-cutoff=int]
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20       [pnmfile]
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22       Minimum  unique abbreviation of option is acceptable.  You may use dou‐
23       ble hyphens instead of single hyphen to denote options.   You  may  use
24       white space in place of the equals sign to separate an option name from
25       its value.
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DESCRIPTION

29       This program is part of Netpbm(1).
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31       pgmmedian applies a median filter to a PGM image, using either the his‐
32       togram sort of select kth value method to determine the median.
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34       See  the  -type  and  -cutoff  options for information on how pgmmedian
35       chooses between the two methods.
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OPTIONS

39       -cutoff int
40              This option provides the cutoff value  that  pgmmedian  uses  to
41              decide  between  using  the  histogram  sort or select kth value
42              method to find the median.
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44              If (maxval / ((width * height) - 1)), where maxval is the maxval
45              of  the  image  and  width  and height are the dimensions of the
46              mask, is less than the cutoff value,  pgmmedian  uses  histogram
47              sort.  Otherwise, it uses kth value.
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49              If  expression  is less than the cutoff, pgmmedian uses the his‐
50              togram sort.  Otherwise it uses the select kth value method.
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52              This option has no effect if you specify -type.
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54              The default is 250
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57       -width=n
58              Width of the median mask to apply.
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60              Default is 3.
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63       -height=n
64              Height of the median mask to apply.
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66              Default is 3.
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69       -type median_type
70              This option selects which method to use to find  median  regard‐
71              less of cutoff value.  Choices are histogram_sort and select.
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73              By  default,  pgmmedian decides which method to use as described
74              under the -cutoff option.
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REFERENCES

80       ·      'Collected Algorithms from ACM'  Volume  II,  Algorithm  489  by
81              Robert W. Floyd
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84       ·      'A  Fast  Two-Dimensional  Median  Filtering Algorithm' in 'IEEE
85              Transactions on Acoustics, Speech, and Signal  Processing'  Vol.
86              ASSP-27, No. 1, February 1979
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89       ·      'Digital Image Processing Algorithms' by Ioannis Pitas, Prentice
90              Hall, 1993 ISBN 0-13-145814-0
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HISTORY

101       pgmmedian was added to Netpbm in Version 10.29 (August 2005).   It  had
102       been  distributed  by  Mike Burns via his own web site before that (and
103       continued to be so).
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AUTHOR

108       Copyright (C) 1996 by Mike Burns <burns@cac.psu.edu>
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112netpbm documentation            28 August 2005        Pgmmedian User Manual(0)