1Pamshuffle User Manual(0) Pamshuffle User Manual(0)
2Updated:
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8 pamshuffle - Shuffle pixels of a Netpbm image
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12 pamshuffle [-column [-randomseed integer]] [pamfile]
13 Minimum unique abbreviations of option are acceptable. You may use
15 double hyphens instead of single hyphen to denote options. You may use
16 white space in place of the equals sign to separate an option name from
17 its value.
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21 This program is part of Netpbm(1).
22 pamshuffle reads a Netpbm image as input and produces an output file
24 with the pixels shuffled. The operation only changes the location of
25 existing pixels; nothing is discarded or added.
26 By default, pixels change location within rows independently, but it is
28 also possible to perform the same shuffle on every row, meaning the
29 program is shuffling vertical columns of pixels. Either way, there is
30 no vertical rearrangement; this means images consisting entirely of
31 horizontal stripes, such as the national banners of Germany, Thailand
32 and Ukraine, will be unchanged.
33 To shuffle vertically, or to perform a complete scramble, use pamshuf‐
35 fle together with pamflip. See examples below.
36 Input is from Standard Input if you don't specify the input file pam‐
38 file.
39 Output is to Standard Output.
41 pamshuffle works on a multi-image stream. It operates on each image in
43 the stream independently and produces a multi-image stream output.
44 The shuffling algorithm is the widely known
46 Fisher-Yates method
47 ⟨https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle⟩ .
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52 In addition to the options common to all programs based on libnetpbm
53 (most notably -quiet, see
54 Common Options ⟨index.html#commonoptions⟩ ), pamshuffle recognizes the
55 following command line options:
56 -column
60 Shuffle vertical columns, i.e. perform the same movement on all
61 rows. Without this option, the program shuffles each row inde‐
62 pendently.
63 -randomseed= integer
66 This is the seed for the random number generator that generates
67 the pixels.
68 Use this to ensure you get the same image on separate invoca‐
70 tions.
71 By default, pamshuffle uses a seed derived from the time of day
73 and process ID, which gives you fairly uncorrelated results in
74 multiple invocations.
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80 In the following example, output is to Standard Output. You will prob‐
81 ably want to add redirection to somewhere useful.
82 •
86 pamshuffle is useful when you want to randomize the orderly out‐
89 put of image generators such as pamseq and pgmramp.
90 Produce five permutations of integers 0 to 15:
92 pgmramp -lr -maxval=15 16 5 | pamshuffle -plain
94 • Shuffle columns:
98 pamshuffle -column image.ppm
100 • Shuffle rows:
105 pamflip -cw image.ppm | pamshuffle | pamflip -ccw
107 • Perform complete shuffle:
111 pamflip -cw image.ppm | pamshuffle | pamflip -ccw | pamshuffle
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120 pamseq(1), pgmramp(1), pamflip(1), ppmshift(1), ppmspread(1), pam(1)
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125 pamshuffle was new in Netpbm 10.99 (June 2022).
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130 By Akira F. Urushibata. Contributed to the public domain by the au‐
131 thor.
132
134 This manual page was generated by the Netpbm tool 'makeman' from HTML
135 source. The master documentation is at
136 http://netpbm.sourceforge.net/doc/pamshuffle.html
138netpbm documentation Pamshuffle User Manual(0)