1UNICHARAMBIGS(5)                                              UNICHARAMBIGS(5)
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NAME

6       unicharambigs - Tesseract unicharset ambiguities
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DESCRIPTION

9       The unicharambigs file (a component of traineddata, see
10       combine_tessdata(1) ) is used by Tesseract to represent possible
11       ambiguities between characters, or groups of characters.
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13       The file contains a number of lines, laid out as follow:
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15           [num] <TAB> [char(s)] <TAB> [num] <TAB> [char(s)] <TAB> [num]
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19       Field one     the number of characters
20                     contained in field two
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22       Field two     the character sequence to
23                     be replaced
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25       Field three   the number of characters
26                     contained in field four
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28       Field four    the character sequence
29                     used to replace field two
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31       Field five    contains either 1 or 0. 1
32                     denotes a mandatory
33                     replacement, 0 denotes an
34                     optional replacement.
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37       Characters appearing in fields two and four should appear in
38       unicharset. The numbers in fields one and three refer to the number of
39       unichars (not bytes).
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EXAMPLE

42           v1
43           2       ' '     1       "     1
44           1       m       2       r n   0
45           3       i i i   1       m     0
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47       The first line is a version identifier. In this example, all instances
48       of the 2 character sequence '' will always be replaced by the 1
49       character sequence "; a 1 character sequence m may be replaced by the 2
50       character sequence rn, and the 3 character sequence may be replaced by
51       the 1 character sequence m.
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53       Version 3.03 and on supports a new, simpler format for the
54       unicharambigs file:
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56           v2
57           '' " 1
58           m rn 0
59           iii m 0
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61       In this format, the "error" and "correction" are simple UTF-8 strings
62       separated by a space, and, after another space, the same type specifier
63       as v1 (0 for optional and 1 for mandatory substitution). Note the
64       downside of this simpler format is that Tesseract has to encode the
65       UTF-8 strings into the components of the unicharset. In complex
66       scripts, this encoding may be ambiguous. In this case, the encoding is
67       chosen such as to use the least UTF-8 characters for each component, ie
68       the shortest unicharset components will make up the encoding.
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HISTORY

71       The unicharambigs file first appeared in Tesseract 3.00; prior to that,
72       a similar format, called DangAmbigs (dangerous ambiguities) was used:
73       the format was almost identical, except only mandatory replacements
74       could be specified, and field 5 was absent.
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BUGS

77       This is a documentation "bug": it’s not currently clear what should be
78       done in the case of ligatures (such as fi) which may also appear as
79       regular letters in the unicharset.
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SEE ALSO

82       tesseract(1), unicharset(5)
83       https://tesseract-ocr.github.io/tessdoc/Training-Tesseract-3.03%E2%80%933.05.html#the-unicharambigs-file
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AUTHOR

86       The Tesseract OCR engine was written by Ray Smith and his research
87       groups at Hewlett Packard (1985-1995) and Google (2006-present).
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91                                  02/25/2022                  UNICHARAMBIGS(5)