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221 lines
7.0 KiB
Groff
221 lines
7.0 KiB
Groff
'\" t
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.\" Title: unicharset
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.\" Author: [see the "AUTHOR" section]
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.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
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.\" Date: 06/12/2015
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.\" Manual: \ \&
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.\" Source: \ \&
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.\" Language: English
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.\"
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.TH "UNICHARSET" "5" "06/12/2015" "\ \&" "\ \&"
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.\" -----------------------------------------------------------------
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.\" * Define some portability stuff
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.\" -----------------------------------------------------------------
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.\" http://bugs.debian.org/507673
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.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.ie \n(.g .ds Aq \(aq
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.el .ds Aq '
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.\" -----------------------------------------------------------------
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.\" * set default formatting
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.\" -----------------------------------------------------------------
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.\" disable hyphenation
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.nh
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.\" disable justification (adjust text to left margin only)
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.ad l
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.\" -----------------------------------------------------------------
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.\" * MAIN CONTENT STARTS HERE *
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.\" -----------------------------------------------------------------
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.SH "NAME"
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unicharset \- character properties file used by tesseract(1)
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.SH "DESCRIPTION"
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.sp
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Tesseract\(cqs unicharset file contains information on each symbol (unichar) the Tesseract OCR engine is trained to recognize\&.
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.sp
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A unicharset file (i\&.e\&. \fIeng\&.unicharset\fR) is distributed as part of a Tesseract language pack (i\&.e\&. \fIeng\&.traineddata\fR)\&. For information on extracting the unicharset file, see combine_tessdata(1)\&.
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.sp
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The first line of a unicharset file contains the number of unichars in the file\&. After this line, each subsequent line provides information for a single unichar\&. The first such line contains a placeholder reserved for the space character\&. Each unichar is referred to within Tesseract by its Unichar ID, which is the line number (minus 1) within the unicharset file\&. Therefore, space gets unichar 0\&.
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.sp
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Each unichar line in the unicharset file (v2+) may have four space\-separated fields:
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.sp
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.if n \{\
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.RS 4
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.\}
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.nf
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\*(Aqcharacter\*(Aq \*(Aqproperties\*(Aq \*(Aqscript\*(Aq \*(Aqid\*(Aq
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.fi
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.if n \{\
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.RE
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.\}
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.sp
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Starting with Tesseract v3\&.02, more information may be given for each unichar:
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.sp
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.if n \{\
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.RS 4
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.\}
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.nf
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\*(Aqcharacter\*(Aq \*(Aqproperties\*(Aq \*(Aqglyph_metrics\*(Aq \*(Aqscript\*(Aq \*(Aqother_case\*(Aq \*(Aqdirection\*(Aq \*(Aqmirror\*(Aq \*(Aqnormed_form\*(Aq
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.fi
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.if n \{\
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.RE
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.\}
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.sp
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Entries:
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.PP
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\fIcharacter\fR
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.RS 4
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The UTF\-8 encoded string to be produced for this unichar\&.
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.RE
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.PP
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\fIproperties\fR
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.RS 4
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An integer mask of character properties, one per bit\&. From least to most significant bit, these are: isalpha, islower, isupper, isdigit, ispunctuation\&.
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.RE
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.PP
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\fIglyph_metrics\fR
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.RS 4
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Ten comma\-separated integers representing various standards for where this glyph is to be found within a baseline\-normalized coordinate system where 128 is normalized to x\-height\&.
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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min_bottom, max_bottom: the ranges where the bottom of the character can be found\&.
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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min_top, max_top: the ranges where the top of the character may be found\&.
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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min_width, max_width: horizontal width of the character\&.
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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min_bearing, max_bearing: how far from the usual start position does the leftmost part of the character begin\&.
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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min_advance, max_advance: how far from the printer\(cqs cell left do we advance to begin the next character\&.
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.RE
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.RE
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.PP
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\fIscript\fR
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.RS 4
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Name of the script (Latin, Common, Greek, Cyrillic, Han, null)\&.
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.RE
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.PP
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\fIother_case\fR
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.RS 4
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The Unichar ID of the other case version of this character (upper or lower)\&.
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.RE
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.PP
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\fIdirection\fR
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.RS 4
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The Unicode BiDi direction of this character, as defined by ICU\(cqs enum UCharDirection\&. (0 = Left to Right, 1 = Right to Left, 2 = European Number\&...)
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.RE
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.PP
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\fImirror\fR
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.RS 4
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The Unichar ID of the BiDirectional mirror of this character\&. For example the mirror of open paren is close paren, but Latin Capital C has no mirror, so it remains a Latin Capital C\&.
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.RE
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.PP
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\fInormed_form\fR
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.RS 4
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The UTF\-8 representation of a "normalized form" of this unichar for the purpose of blaming a module for errors given ground truth text\&. For instance, a left or right single quote may normalize to an ASCII quote\&.
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.RE
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.SH "EXAMPLE (V2)"
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.sp
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.if n \{\
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.RS 4
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.\}
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.nf
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; 10 Common 46
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b 3 Latin 59
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W 5 Latin 40
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7 8 Common 66
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= 0 Common 93
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.fi
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.if n \{\
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.RE
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.\}
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.sp
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";" is a punctuation character\&. Its properties are thus represented by the binary number 10000 (10 in hexadecimal)\&.
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.sp
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"b" is an alphabetic character and a lower case character\&. Its properties are thus represented by the binary number 00011 (3 in hexadecimal)\&.
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.sp
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"W" is an alphabetic character and an upper case character\&. Its properties are thus represented by the binary number 00101 (5 in hexadecimal)\&.
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.sp
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"7" is just a digit\&. Its properties are thus represented by the binary number 01000 (8 in hexadecimal)\&.
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.sp
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"=" is not punctuation nor a digit nor an alphabetic character\&. Its properties are thus represented by the binary number 00000 (0 in hexadecimal)\&.
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.sp
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Japanese or Chinese alphabetic character properties are represented by the binary number 00001 (1 in hexadecimal): they are alphabetic, but neither upper nor lower case\&.
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.SH "EXAMPLE (V3.02)"
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.sp
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.if n \{\
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.RS 4
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.\}
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.nf
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110
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NULL 0 NULL 0
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N 5 59,68,216,255,87,236,0,27,104,227 Latin 11 0 1 N
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Y 5 59,68,216,255,91,205,0,47,91,223 Latin 33 0 2 Y
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1 8 59,69,203,255,45,128,0,66,74,173 Common 3 2 3 1
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9 8 18,66,203,255,89,156,0,39,104,173 Common 4 2 4 9
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a 3 58,65,186,198,85,164,0,26,97,185 Latin 56 0 5 a
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\&. \&. \&.
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.fi
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.if n \{\
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.RE
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.\}
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.SH "CAVEATS"
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.sp
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Although the unicharset reader maintains the ability to read unicharsets of older formats and will assign default values to missing fields, the accuracy will be degraded\&.
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.sp
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Further, most other data files are indexed by the unicharset file, so changing it without re\-generating the others is likely to have dire consequences\&.
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.SH "HISTORY"
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.sp
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The unicharset format first appeared with Tesseract 2\&.00, which was the first version to support languages other than English\&. The unicharset file contained only the first two fields, and the "ispunctuation" property was absent (punctuation was regarded as "0", as "=" is in the above example\&.
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.SH "SEE ALSO"
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.sp
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tesseract(1), combine_tessdata(1), unicharset_extractor(1)
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.sp
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\m[blue]\fBhttps://github\&.com/tesseract\-ocr/tesseract/wiki/TrainingTesseract\fR\m[]
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.SH "AUTHOR"
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.sp
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The Tesseract OCR engine was written by Ray Smith and his research groups at Hewlett Packard (1985\-1995) and Google (2006\-present)\&.
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