TESSERACT(1)TESSERACT(1)NAMEtesseract - command-line OCR engine
SYNOPSIStesseract imagename outbase [-l lang] [-psm N] [configfile ...]
DESCRIPTIONtesseract(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.
OPTIONS
imagename
The name of the input image. Most image file formats (anything
readable by Leptonica) are supported.
outbase
The basename of the output file (to which the appropriate extension
will be appended). By default the output will be named outbase.txt.
-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.
-v
Returns the current version of the tesseract(1) executable.
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.
Nota Bene: The options -l lang and -psm N must occur before any
configfile.
LANGUAGES
There are currently language packs available for the following
languages:
ara (Arabic), aze (Azerbauijani), bul (Bulgarian), cat (Catalan), ces
(Czech), chi_sim (Simplified Chinese), chi_tra (Traditional Chinese),
chr (Cherokee), dan (Danish), dan-frak (Danish (Fraktur)), deu
(German), ell (Greek), eng (English), enm (Old English), epo
(Esperanto), est (Estonian), fin (Finnish), fra (French), frm (Old
French), glg (Galician), heb (Hebrew), hin (Hindi), hrv (Croation), hun
(Hungarian), ind (Indonesian), ita (Italian), jpn (Japanese), kor
(Korean), lav (Latvian), lit (Lithuanian), nld (Dutch), nor
(Norwegian), pol (Polish), por (Portuguese), ron (Romanian), rus
(Russian), slk (Slovakian), slv (Slovenian), sqi (Albanian), spa
(Spanish), srp (Serbian), swe (Swedish), tam (Tamil), tel (Telugu), tgl
(Tagalog), tha (Thai), tur (Turkish), ukr (Ukrainian), vie (Vietnamese)
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.
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:
the
quick
brown
fox
jumped
/path/to/eng.user-patterns:
1-\d\d\d-GOOG-411
www.\n\\\*.com
/path/to/configs/bazaar:
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 http://www.isri.unlv.edu/downloads/AT-1995.pdf. With Tesseract
2.00, scripts are now included to allow anyone to reproduce some of
these tests. See
http://code.google.com/p/tesseract-ocr/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: http://code.google.com/p/tesseract-ocr/ Information on
training:
http://code.google.com/p/tesseract-ocr/wiki/TrainingTesseract3
SEE ALSOambiguous_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
04/09/2012 TESSERACT(1)
