.ie \n(.g .ds Aq \(aq

.el .ds Aq '

.nh

.ad l

unicharset \- character properties file used by tesseract(1)

.sp

Tesseract\(cqs unicharset file contains information on each symbol (unichar) the Tesseract OCR engine is trained to recognize\&.

.sp

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)\&.

.sp

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\&.

.sp

Each unichar line in the unicharset file (v2+) may have four space\-separated fields:

.sp

.if n \{\

.RS 4

.\}

.nf

\*(Aqcharacter\*(Aq \*(Aqproperties\*(Aq \*(Aqscript\*(Aq \*(Aqid\*(Aq

.fi

.if n \{\

.RE

.\}

.sp

Starting with Tesseract v3\&.02, more information may be given for each unichar:

.sp

.if n \{\

.RS 4

.\}

.nf

\*(Aqcharacter\*(Aq \*(Aqproperties\*(Aq \*(Aqglyph_metrics\*(Aq \*(Aqscript\*(Aq \*(Aqother_case\*(Aq \*(Aqdirection\*(Aq \*(Aqmirror\*(Aq \*(Aqnormed_form\*(Aq

.fi

.if n \{\

.RE

.\}

.sp

Entries:

.PP

.RS 4

The UTF\-8 encoded string to be produced for this unichar\&.

.RE

.PP

.RS 4

An integer mask of character properties, one per bit\&. From least to most significant bit, these are: isalpha, islower, isupper, isdigit, ispunctuation\&.

.RE

.PP

.RS 4

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\&.

.sp

.RS 4

.ie n \{\

.\}

.el \{\

.sp -1

.IP \(bu 2.3

.\}

min_bottom, max_bottom: the ranges where the bottom of the character can be found\&.

.RE

.sp

.RS 4

.ie n \{\

.\}

.el \{\

.sp -1

.IP \(bu 2.3

.\}

min_top, max_top: the ranges where the top of the character may be found\&.

.RE

.sp

.RS 4

.ie n \{\

.\}

.el \{\

.sp -1

.IP \(bu 2.3

.\}

min_width, max_width: horizontal width of the character\&.

.RE

.sp

.RS 4

.ie n \{\

.\}

.el \{\

.sp -1

.IP \(bu 2.3

.\}

min_bearing, max_bearing: how far from the usual start position does the leftmost part of the character begin\&.

.RE

.sp

.RS 4

.ie n \{\

.\}

.el \{\

.sp -1

.IP \(bu 2.3

.\}

min_advance, max_advance: how far from the printer\(cqs cell left do we advance to begin the next character\&.

.RE

.RE

.PP

.RS 4

Name of the script (Latin, Common, Greek, Cyrillic, Han, null)\&.

.RE

.PP

.RS 4

The Unichar ID of the other case version of this character (upper or lower)\&.

.RE

.PP

.RS 4

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\&...)

.RE

.PP

.RS 4

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\&.

.RE

.PP

.RS 4

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\&.

.RE

.sp

.if n \{\

.RS 4

.\}

.nf

; 10 Common 46

b 3 Latin 59

W 5 Latin 40

7 8 Common 66

= 0 Common 93

.fi

.if n \{\

.RE

.\}

.sp

";" is a punctuation character\&. Its properties are thus represented by the binary number 10000 (10 in hexadecimal)\&.

.sp

"b" is an alphabetic character and a lower case character\&. Its properties are thus represented by the binary number 00011 (3 in hexadecimal)\&.

.sp

"W" is an alphabetic character and an upper case character\&. Its properties are thus represented by the binary number 00101 (5 in hexadecimal)\&.

.sp

"7" is just a digit\&. Its properties are thus represented by the binary number 01000 (8 in hexadecimal)\&.

.sp

"=" is not punctuation nor a digit nor an alphabetic character\&. Its properties are thus represented by the binary number 00000 (0 in hexadecimal)\&.

.sp

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\&.

.sp

.if n \{\

.RS 4

.\}

.nf

110

NULL 0 NULL 0

N 5 59,68,216,255,87,236,0,27,104,227 Latin 11 0 1 N

Y 5 59,68,216,255,91,205,0,47,91,223 Latin 33 0 2 Y

1 8 59,69,203,255,45,128,0,66,74,173 Common 3 2 3 1

9 8 18,66,203,255,89,156,0,39,104,173 Common 4 2 4 9

a 3 58,65,186,198,85,164,0,26,97,185 Latin 56 0 5 a

\&. \&. \&.

.fi

.if n \{\

.RE

.\}

.sp

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\&.

.sp

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\&.

.sp

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\&.

.sp

tesseract(1), combine_tessdata(1), unicharset_extractor(1)

.sp

.sp

The Tesseract OCR engine was written by Ray Smith and his research groups at Hewlett Packard (1985\-1995) and Google (2006\-present)\&.