1Pgmmedian User Manual(0) Pgmmedian User Manual(0)
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6 pgmmedian - apply a median filter to a PGM file
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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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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 or 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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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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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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97 pgmnoise(1), pamaddnoise(1), pgm(1)
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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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108 Copyright (C) 1996 by Mike Burns <burns@cac.psu.edu>
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112netpbm documentation 28 August 2005 Pgmmedian User Manual(0)