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 For most images, no command-line options need to be specified. The fol‐
46 lowing options are available, however, for unusual circumstances:
47 --invert
51 Swap the left- and right-eye
52 images. pamsistoaglyph assumes that its input
53 represents a wall-eyed stereogram and generates the
54 anaglyphic
55 image accordingly. If the generated image appears to recede
56 into
57 the page where it should pop out of the page (and vice
58 versa),
59 this typically implies that the input image represents a
60 cross-eyed stereogram. Use --invert to correct
61 the image depth.
62 --sep=number
65 Specify the distance in pixels between the left- and right-eye
66 images. Essentially, this corresponds to the distance
67 between
68 repetitions of the background pattern. The --sep
69 option should rarely be necessary
70 as pamsistoaglyph is fairly good at determining
71 automatically the eye-separation distance.
72 --minsep=number
75 This option is similar to --sep but
76 constrains pamsistoaglyph only to
77 a minimum eye-separation distance. Any distance larger
78 than number is acceptable. The --minsep
79 option should rarely be necessary
80 as pamsistoaglyph is fairly good at determining
81 automatically the eye-separation distance. The default
82 value for
83 the minimum eye-separation distance is 10% of the image
84 width;
85 this value seems to work well in practice.
86 --gray=number
89 Limit the number of gray levels to use when searching for the
90 optimal eye-separation
91 distance. Because pamsistoaglyph looks for
92 repeated patterns, it is vulnerable to being confused by
93 slight
94 variations in color. By reducing the input image to
95 grayscale and
96 capping the number of gray levels,
97 pamsistoaglyph ameliorates the effects of
98 unintentional color variations (such as those caused by con‐
99 version
100 from a low-quality JPEG image, for example). The default of
101 63
102 seems to work well so the --gray option should
103 rarely be necessary.
104
109 The registration algorithm used by pamsistoaglyph was developed specif‐
110 ically for this program. As far as the author knows, there are no
111 existing algorithms for converting stereograms to anaglyphs. The algo‐
112 rithm works as follows:
113 · Convert the image to grayscale to increase the ability to iden‐
117 tify
118 matches.
119 · Count the number of pixels that match N pixels ahead in the
122 image for all N in [1, width/2].
123 · Maintain a running mean (mu) and standard deviation (sigma) of
126 the number of matched pixels.
127 · Store the N corresponding to each spike in the number of
130 matched pixels. A spike is defined as a tally that exceeds
131 the
132 mean plus one, two, or three standard deviations. Only the
133 first
134 spike of a given standard-deviation multiplier is stored.
135 · If a tally greater than mu+3sigma was encountered, return the
138 corresponding N. If not, then if a tally greater than
139 mu+2sigma was encountered, return the
140 corresponding N. If not, then if a tally greater than
141 mu+sigma was encountered, return the
142 corresponding N. If not, then return the N that
143 produces the minimum average distance between matched pixels
144 (i.e., #matches divided by #pixels). If no
145 such N exceeds the minimum allowable eye-separation value,
146 return zero to indicate failure.
147 · If the algorithm returned zero, rerun the algorithm indepen‐
150 dently
151 on each row of the input image and return the median of
152 all N that exceed the minimum allowable eye-separation
153 value. If no such N exists, abort with an error
154 message.
155
159 Scott Pakin wrote pamsistoaglyph in April 2009. It first appeared in
160 Netpbm in Release 10.47 (June 2009).
161
165 Copyright (C) 2009 Scott Pakin, scott+pbm@pakin.org.
166
170 ·
171 pamstereogram(1)
173 ·
175 ppm3d(1),
177 ·
179 http://en.wikipedia.org/wiki/Stereogram
181 ⟨http://en.wikipedia.org/wiki/Stereogram⟩
182
184 This manual page was generated by the Netpbm tool 'makeman' from HTML
185 source. The master documentation is at
186 http://netpbm.sourceforge.net/doc/pamsistoaglyph.html
188netpbm documentation 5 April 2009 Pamsistoaglyph User Manual(0)