'\" t
.\"     Title: unicharambigs
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 01/11/2023
.\"    Manual: \ \&
.\"    Source: \ \&
.\"  Language: English
.\"
.TH "UNICHARAMBIGS" "5" "01/11/2023" "\ \&" "\ \&"
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.SH "NAME"
unicharambigs \- Tesseract unicharset ambiguities
.SH "DESCRIPTION"
.sp
The unicharambigs file (a component of traineddata, see combine_tessdata(1) ) is used by Tesseract to represent possible ambiguities between characters, or groups of characters\&.
.sp
The file contains a number of lines, laid out as follow:
.sp
.if n \{\
.RS 4
.\}
.nf
[num] <TAB> [char(s)] <TAB> [num] <TAB> [char(s)] <TAB> [num]
.fi
.if n \{\
.RE
.\}
.sp
.TS
tab(:);
lt lt
lt lt
lt lt
lt lt
lt lt.
T{
.sp
Field one
T}:T{
.sp
the number of characters contained in field two
T}
T{
.sp
Field two
T}:T{
.sp
the character sequence to be replaced
T}
T{
.sp
Field three
T}:T{
.sp
the number of characters contained in field four
T}
T{
.sp
Field four
T}:T{
.sp
the character sequence used to replace field two
T}
T{
.sp
Field five
T}:T{
.sp
contains either 1 or 0\&. 1 denotes a mandatory replacement, 0 denotes an optional replacement\&.
T}
.TE
.sp 1
.sp
Characters appearing in fields two and four should appear in unicharset\&. The numbers in fields one and three refer to the number of unichars (not bytes)\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
v1
2       \*(Aq \*(Aq     1       "     1
1       m       2       r n   0
3       i i i   1       m     0
.fi
.if n \{\
.RE
.\}
.sp
The first line is a version identifier\&. In this example, all instances of the \fI2\fR character sequence \fI\*(Aq\fR\*(Aq will \fBalways\fR be replaced by the \fI1\fR character sequence \fI"\fR; a \fI1\fR character sequence \fIm\fR \fBmay\fR be replaced by the \fI2\fR character sequence \fIrn\fR, and the \fI3\fR character sequence \fBmay\fR be replaced by the \fI1\fR character sequence \fIm\fR\&.
.sp
Version 3\&.03 and on supports a new, simpler format for the unicharambigs file:
.sp
.if n \{\
.RS 4
.\}
.nf
v2
\*(Aq\*(Aq " 1
m rn 0
iii m 0
.fi
.if n \{\
.RE
.\}
.sp
In this format, the "error" and "correction" are simple UTF\-8 strings separated by a space, and, after another space, the same type specifier as v1 (0 for optional and 1 for mandatory substitution)\&. Note the downside of this simpler format is that Tesseract has to encode the UTF\-8 strings into the components of the unicharset\&. In complex scripts, this encoding may be ambiguous\&. In this case, the encoding is chosen such as to use the least UTF\-8 characters for each component, ie the shortest unicharset components will make up the encoding\&.
.SH "HISTORY"
.sp
The unicharambigs file first appeared in Tesseract 3\&.00; prior to that, a similar format, called DangAmbigs (\fIdangerous ambiguities\fR) was used: the format was almost identical, except only mandatory replacements could be specified, and field 5 was absent\&.
.SH "BUGS"
.sp
This is a documentation "bug": it\(cqs not currently clear what should be done in the case of ligatures (such as \fIfi\fR) which may also appear as regular letters in the unicharset\&.
.SH "SEE ALSO"
.sp
tesseract(1), unicharset(5) \m[blue]\fBhttps://tesseract\-ocr\&.github\&.io/tessdoc/Training\-Tesseract\-3\&.03%E2%80%933\&.05\&.html#the\-unicharambigs\-file\fR\m[]
.SH "AUTHOR"
.sp
The Tesseract OCR engine was written by Ray Smith and his research groups at Hewlett Packard (1985\-1995) and Google (2006\-present)\&.