tesseract/doc/tesseract.1.asc

TESSERACT(1)
============
:doctype: manpage

NAME
----
tesseract - command-line OCR engine

SYNOPSIS
--------
*tesseract* 'imagename'|'stdin' 'outputbase'|'stdout' [options...] [configfile...]

DESCRIPTION
-----------
tesseract(1) is a commercial quality OCR engine originally developed at HP
between 1985 and 1995. In 1995, this engine was among the top 3 evaluated by
UNLV. It was open-sourced by HP and UNLV in 2005, and has been developed
at Google since then.


IN/OUT ARGUMENTS
----------------
'imagename'::
	The name of the input image.  Most image file formats (anything
	readable by Leptonica) are supported.

'stdin'::
	Instruction to read data from standard input

'outputbase'::
	The basename of the output file (to which the appropriate extension
	will be appended).  By default the output will be named 'outbase.txt'.

'stdout'::
	Instruction to sent output data to standard output


OPTIONS
-------
'--tessdata-dir /path'::
	Specify the location of tessdata path

'--user-words /path/to/file'::
	Specify the location of user words file

'--user-patterns /path/to/file'::
	Specify the location of user patterns file

'-c configvar=value'::
	Set value for control parameter. Multiple -c arguments are allowed.

'-l lang'::
	The language to use. If none is specified, English is assumed.
	Multiple languages may be specified, separated by plus characters.
	Tesseract uses 3-character ISO 639-2 language codes. (See LANGUAGES)

'--psm N'::
	Set Tesseract to only run a subset of layout analysis and assume
	a certain form of image. The options for *N* are:

	0 = Orientation and script detection (OSD) only.
	1 = Automatic page segmentation with OSD.
	2 = Automatic page segmentation, but no OSD, or OCR.
	3 = Fully automatic page segmentation, but no OSD. (Default)
	4 = Assume a single column of text of variable sizes.
	5 = Assume a single uniform block of vertically aligned text.
	6 = Assume a single uniform block of text.
	7 = Treat the image as a single text line.
	8 = Treat the image as a single word.
	9 = Treat the image as a single word in a circle.
	10 = Treat the image as a single character.

'--oem N'::
	Specify OCR Engine mode. The options for *N* are:

	0 = Original Tesseract only.
	1 = Neural nets LSTM only.
	2 = Tesseract + LSTM.
	3 = Default, based on what is available.

'configfile'::
	The name of a config to use. A config is a plaintext file which
	contains a list of variables and their values, one per line, with a
	space separating variable from value.  Interesting config files
	include: +
  * hocr - Output in hOCR format instead of as a text file.
  * pdf  - Output in pdf instead of a text file.

*Nota Bene:*   The options '-l lang' and '--psm N' must occur
before any 'configfile'.


SINGLE OPTIONS
--------------
'-h, --help'::
	Show help message.

'--help-psm'::
	Show page segmentation modes.

'--help-oem'::
	Show OCR Engine modes.

'-v, --version'::
	Returns the current version of the tesseract(1) executable.

'--list-langs'::
	List available languages for tesseract engine. Can be used with --tessdata-dir.

'--print-parameters'::
	Print tesseract parameters.



LANGUAGES
---------

The currently available traineddata files for tesseract 4.0
for the following languages are in
(in https://github.com/tesseract-ocr/tessdata_fast):

*afr* (Afrikaans),
*amh* (Amharic),
*ara* (Arabic),
*asm* (Assamese),
*aze* (Azerbaijani),
*aze_cyrl* (Azerbaijani - Cyrilic),
*bel* (Belarusian),
*ben* (Bengali),
*bod* (Tibetan),
*bos* (Bosnian),
*bre* (Breton),
*bul* (Bulgarian),
*cat* (Catalan; Valencian),
*ceb* (Cebuano),
*ces* (Czech),
*chi_sim* (Chinese - Simplified),
*chi_tra* (Chinese - Traditional),
*chr* (Cherokee),
*cym* (Welsh),
*dan* (Danish),
*deu* (German),
*dzo* (Dzongkha),
*ell* (Greek, Modern (1453-)),
*eng* (English),
*enm* (English, Middle (1100-1500)),
*epo* (Esperanto),
*equ* (Math / equation detection module),
*est* (Estonian),
*eus* (Basque),
*fas* (Persian),
*fin* (Finnish),
*fra* (French),
*frk* (Frankish),
*frm* (French, Middle (ca.1400-1600)),
*gle* (Irish),
*glg* (Galician),
*grc* (Greek, Ancient (to 1453)),
*guj* (Gujarati),
*hat* (Haitian; Haitian Creole),
*heb* (Hebrew),
*hin* (Hindi),
*hrv* (Croatian),
*hun* (Hungarian),
*iku* (Inuktitut),
*ind* (Indonesian),
*isl* (Icelandic),
*ita* (Italian),
*ita_old* (Italian - Old),
*jav* (Javanese),
*jpn* (Japanese),
*kan* (Kannada),
*kat* (Georgian),
*kat_old* (Georgian - Old),
*kaz* (Kazakh),
*khm* (Central Khmer),
*kir* (Kirghiz; Kyrgyz),
*kor* (Korean),
*kor_vert* (Korean (vertical)),
*kur* (Kurdish),
*kur_ara* (Kurdish (Arabic)),
*lao* (Lao),
*lat* (Latin),
*lav* (Latvian),
*lit* (Lithuanian),
*ltz* (Luxembourgish),
*mal* (Malayalam),
*mar* (Marathi),
*mkd* (Macedonian),
*mlt* (Maltese),
*mon* (Mongolian),
*mri* (Maori),
*msa* (Malay),
*mya* (Burmese),
*nep* (Nepali),
*nld* (Dutch; Flemish),
*nor* (Norwegian),
*oci* (Occitan (post 1500)),
*ori* (Oriya),
*osd* (Orientation and script detection module),
*pan* (Panjabi; Punjabi),
*pol* (Polish),
*por* (Portuguese),
*pus* (Pushto; Pashto),
*que* (Quechua),
*ron* (Romanian; Moldavian; Moldovan),
*rus* (Russian),
*san* (Sanskrit),
*sin* (Sinhala; Sinhalese),
*slk* (Slovak),
*slv* (Slovenian),
*snd* (Sindhi),
*spa* (Spanish; Castilian),
*spa_old* (Spanish; Castilian - Old),
*sqi* (Albanian),
*srp* (Serbian),
*srp_latn* (Serbian - Latin),
*sun* (Sundanese),
*swa* (Swahili),
*swe* (Swedish),
*syr* (Syriac),
*tam* (Tamil),
*tat* (Tatar),
*tel* (Telugu),
*tgk* (Tajik),
*tgl* (Tagalog),
*tha* (Thai),
*tir* (Tigrinya),
*ton* (Tonga),
*tur* (Turkish),
*uig* (Uighur; Uyghur),
*ukr* (Ukrainian),
*urd* (Urdu),
*uzb* (Uzbek),
*uzb_cyrl* (Uzbek - Cyrilic),
*vie* (Vietnamese),
*yid* (Yiddish),
*yor* (Yoruba)

To use a non-standard language pack named *foo.traineddata*, set the
*TESSDATA_PREFIX* environment variable so the file can be found at
*TESSDATA_PREFIX*/tessdata/*foo*.traineddata and give Tesseract the
argument '-l foo'.

SCRIPTS
-------

The traineddata files for the following scripts for tesseract 4.0
are also in https://github.com/tesseract-ocr/tessdata_fast. 

In most cases, each of these contains all the languages that use that script PLUS English. 
So it is possible to recognize a language that has not been specifically trained for 
by using traineddata for the script it is written in.

Arabic, 
Armenian, 
Bengali, 
Canadian Aboriginal, 
Cherokee, 
Cyrillic, 
Devanagari, 
Ethiopic, 
Fraktur, 
Georgian, 
Greek, 
Gujarati, 
Gurmukhi, 
Han - Simplified, 
Han - Simplified (vertical), 
Han - Traditional, 
Han - Traditional (vertical), 
Hangul, 
Hangul (vertical), 
Hebrew, 
Japanese, 
Japanese (vertical), 
Kannada, 
Khmer, 
Lao, 
Latin, 
Malayalam, 
Myanmar, 
Oriya (Odia), 
Sinhala, 
Syriac, 
Tamil, 
Telugu, 
Thaana, 
Thai, 
Tibetan, 
Vietnamese.


CONFIG FILES AND AUGMENTING WITH USER DATA
------------------------------------------

Tesseract config files consist of lines with variable-value pairs (space
separated).  The variables are documented as flags in the source code like
the following one in tesseractclass.h:

STRING_VAR_H(tessedit_char_blacklist, "",
             "Blacklist of chars not to recognize");

These variables may enable or disable various features of the engine, and
may cause it to load (or not load) various data.  For instance, let's suppose
you want to OCR in English, but suppress the normal dictionary and load an
alternative word list and an alternative list of patterns -- these two files
are the most commonly used extra data files.

If your language pack is in /path/to/eng.traineddata  and the hocr config
is in /path/to/configs/hocr then create three new files:

/path/to/eng.user-words:
[verse]
the
quick
brown
fox
jumped


/path/to/eng.user-patterns:
[verse]
1-\d\d\d-GOOG-411
www.\n\\\*.com

/path/to/configs/bazaar:
[verse]
load_system_dawg     F
load_freq_dawg       F
user_words_suffix    user-words
user_patterns_suffix user-patterns

Now, if you pass the word 'bazaar' as a trailing command line parameter
to Tesseract, Tesseract will not bother loading the system dictionary nor
the dictionary of frequent words and will load and use the eng.user-words
and eng.user-patterns files you provided.  The former is a simple word list,
one per line.  The format of the latter is documented in dict/trie.h
on read_pattern_list().


HISTORY
-------
The engine was developed at Hewlett Packard Laboratories Bristol and at
Hewlett Packard Co, Greeley Colorado between 1985 and 1994, with some more
changes made in 1996 to port to Windows, and some $$C++$$izing in 1998. A
lot of the code was written in C, and then some more was written in $$C++$$.
The $$C++$$ code makes heavy use of a list system using macros. This predates
stl, was portable before stl, and is more efficient than stl lists, but has
the big negative that if you do get a segmentation violation, it is hard to
debug.

Version 2.00 brought Unicode (UTF-8) support, six languages, and the ability
to train Tesseract.

Tesseract was included in UNLV's Fourth Annual Test of OCR Accuracy.
See <https://github.com/tesseract-ocr/docs/blob/master/AT-1995.pdf>. With Tesseract 2.00,
scripts are now included to allow anyone to reproduce some of these tests.
See <https://github.com/tesseract-ocr/tesseract/wiki/TestingTesseract> for more
details.

Tesseract 3.00 adds a number of new languages, including Chinese, Japanese,
and Korean. It also introduces a new, single-file based system of managing
language data.

Tesseract 3.02 adds BiDirectional text support, the ability to recognize
multiple languages in a single image, and improved layout analysis.

For further details, see the file ReleaseNotes included with the distribution.

RESOURCES
---------
Main web site: <https://github.com/tesseract-ocr> +
Information on training: <https://github.com/tesseract-ocr/tesseract/wiki/TrainingTesseract>

SEE ALSO
--------
ambiguous_words(1), cntraining(1), combine_tessdata(1), dawg2wordlist(1),
shape_training(1), mftraining(1), unicharambigs(5), unicharset(5),
unicharset_extractor(1), wordlist2dawg(1)

AUTHOR
------
Tesseract development was led at Hewlett-Packard and Google by Ray Smith.
The development team has included:

Ahmad Abdulkader, Chris Newton, Dan Johnson, Dar-Shyang Lee, David Eger,
Eric Wiseblatt, Faisal Shafait, Hiroshi Takenaka, Joe Liu, Joern Wanke,
Mark Seaman, Mickey Namiki, Nicholas Beato, Oded Fuhrmann, Phil Cheatle,
Pingping Xiu, Pong Eksombatchai (Chantat), Ranjith Unnikrishnan, Raquel
Romano, Ray Smith, Rika Antonova, Robert Moss, Samuel Charron, Sheelagh
Lloyd, Shobhit Saxena, and Thomas Kielbus.

COPYING
-------
Licensed under the Apache License, Version 2.0