1Pamsistoaglyph User Manual(0) Pamsistoaglyph User Manual(0)
2
6 pamsistoaglyph - convert a single-image stereogram to a red/cyan
7 anaglyphic image
8
12 pamsistoaglyph [--invert] [--sep=number] [--minsep=number] [--gray=num‐
13 ber] [in_netpbmfile
14 All options can be abbreviated to their shortest unique prefix. You may
17 use either white space or an equals sign between an option name and its
18 value.
19
23 This program is part of Netpbm(1).
24 pamsistoaglyph reads a Netpbm image as input and produces a Netpbm
26 image as output.
27 pamsistoaglyph takes a single-image stereogram (SIS) such as those pro‐
29 duced by pamstereogram(1) and converts it to a red/cyan anaglyphic
30 image such as those produced by ppm3d(1). Many people have trouble
31 tricking their eyes into focusing beyond the image in front of them and
32 are therefore unable to perceive the 3-D shape hidden within a single-
33 image stereogram. Anaglyphic stereograms are easier to perceive in 3-D
34 but require a pair of red/cyan glasses such as those often used to
35 watch 3-D movies. The goal of pamsistoaglyph is to help people who have
36 trouble viewing single-image stereograms see the intriguing 3-D effect.
37 pamsistoaglyph can convert single-image random-dot stereograms (SIRDS),
39 wallpaper stereograms, and even dual-image stereograms to anaglyphic
40 images.
41
45 In addition to the options common to all programs based on libnetpbm
46 (most notably -quiet, see
47 Common Options ⟨index.html#commonoptions⟩ ), pamsistoaglyph recognizes
48 the following command line options:
49 For most images, no command-line options need to be specified. The
51 following options are available, however, for unusual circumstances.
52 --invert
56 Swap the left- and right-eye
57 images. pamsistoaglyph assumes that its input
58 represents a wall-eyed stereogram and generates the
59 anaglyphic
60 image accordingly. If the generated image appears to recede
61 into
62 the page where it should pop out of the page (and vice
63 versa),
64 this typically implies that the input image represents a
65 cross-eyed stereogram. Use --invert to correct
66 the image depth.
67 --sep=number
70 Specify the distance in pixels between the left- and right-eye
71 images. Essentially, this corresponds to the distance
72 between
73 repetitions of the background pattern. The --sep
74 option should rarely be necessary
75 as pamsistoaglyph is fairly good at determining
76 automatically the eye-separation distance.
77 --minsep=number
80 This option is similar to --sep but
81 constrains pamsistoaglyph only to
82 a minimum eye-separation distance. Any distance larger
83 than number is acceptable. The --minsep
84 option should rarely be necessary
85 as pamsistoaglyph is fairly good at determining
86 automatically the eye-separation distance. The default
87 value for
88 the minimum eye-separation distance is 10% of the image
89 width;
90 this value seems to work well in practice.
91 --gray=number
94 Limit the number of gray levels to use when searching for the
95 optimal eye-separation
96 distance. Because pamsistoaglyph looks for
97 repeated patterns, it is vulnerable to being confused by
98 slight
99 variations in color. By reducing the input image to
100 grayscale and
101 capping the number of gray levels,
102 pamsistoaglyph ameliorates the effects of
103 unintentional color variations (such as those caused by con‐
104 version
105 from a low-quality JPEG image, for example). The default of
106 63
107 seems to work well so the --gray option should
108 rarely be necessary.
109
114 The registration algorithm used by pamsistoaglyph was developed specif‐
115 ically for this program. As far as the author knows, there are no
116 existing algorithms for converting stereograms to anaglyphs. The algo‐
117 rithm works as follows:
118 · Convert the image to grayscale to increase the ability to iden‐
122 tify
123 matches.
124 · Count the number of pixels that match N pixels ahead in the
127 image for all N in [1, width/2].
128 · Maintain a running mean (mu) and standard deviation (sigma) of
131 the number of matched pixels.
132 · Store the N corresponding to each spike in the number of
135 matched pixels. A spike is defined as a tally that exceeds
136 the
137 mean plus one, two, or three standard deviations. Only the
138 first
139 spike of a given standard-deviation multiplier is stored.
140 · If a tally greater than mu+3sigma was encountered, return the
143 corresponding N. If not, then if a tally greater than
144 mu+2sigma was encountered, return the
145 corresponding N. If not, then if a tally greater than
146 mu+sigma was encountered, return the
147 corresponding N. If not, then return the N that
148 produces the minimum average distance between matched pixels
149 (i.e., #matches divided by #pixels). If no
150 such N exceeds the minimum allowable eye-separation value,
151 return zero to indicate failure.
152 · If the algorithm returned zero, rerun the algorithm indepen‐
155 dently
156 on each row of the input image and return the median of
157 all N that exceed the minimum allowable eye-separation
158 value. If no such N exists, abort with an error
159 message.
160
164 Scott Pakin wrote pamsistoaglyph in April 2009. It first appeared in
165 Netpbm in Release 10.47 (June 2009).
166
170 Copyright (C) 2009 Scott Pakin, scott+pbm@pakin.org.
171
175 ·
176 pamstereogram(1)
178 ·
180 ppm3d(1),
182 ·
184 http://en.wikipedia.org/wiki/Stereogram
186 ⟨http://en.wikipedia.org/wiki/Stereogram⟩
187
189 This manual page was generated by the Netpbm tool 'makeman' from HTML
190 source. The master documentation is at
191 http://netpbm.sourceforge.net/doc/pamsistoaglyph.html
193netpbm documentation 5 April 2009 Pamsistoaglyph User Manual(0)