tesseract - Online in the Cloud

PROGRAM:

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.

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

-v
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 to the stdout.

LANGUAGES

There are currently language packs available for the following languages (in
https://github.com/tesseract-ocr/tessdata):

afr (Afrikaans) amh (Amharic) ara (Arabic) asm (Assamese) aze (Azerbaijani) aze_cyrl
(Azerbaijani - Cyrilic) bel (Belarusian) ben (Bengali) bod (Tibetan) bos (Bosnian) bul
(Bulgarian) cat (Catalan; Valencian) ceb (Cebuano) ces (Czech) chi_sim (Chinese -
Simplified) chi_tra (Chinese - Traditional) chr (Cherokee) cym (Welsh) dan (Danish)
dan_frak (Danish - Fraktur) deu (German) deu_frak (German - Fraktur) 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) kur (Kurdish) lao (Lao) lat (Latin) lav (Latvian) lit
(Lithuanian) mal (Malayalam) mar (Marathi) mkd (Macedonian) mlt (Maltese) msa (Malay) mya
(Burmese) nep (Nepali) nld (Dutch; Flemish) nor (Norwegian) ori (Oriya) osd (Orientation
and script detection module) pan (Panjabi; Punjabi) pol (Polish) por (Portuguese) pus
(Pushto; Pashto) ron (Romanian; Moldavian; Moldovan) rus (Russian) san (Sanskrit) sin
(Sinhala; Sinhalese) slk (Slovak) slk_frak (Slovak - Fraktur) slv (Slovenian) spa
(Spanish; Castilian) spa_old (Spanish; Castilian - Old) sqi (Albanian) srp (Serbian)
srp_latn (Serbian - Latin) swa (Swahili) swe (Swedish) syr (Syriac) tam (Tamil) tel
(Telugu) tgk (Tajik) tgl (Tagalog) tha (Thai) tir (Tigrinya) tur (Turkish) uig (Uighur;
Uyghur) ukr (Ukrainian) urd (Urdu) uzb (Uzbek) uzb_cyrl (Uzbek - Cyrilic) vie (Vietnamese)
yid (Yiddish)

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
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

Use tesseract online using onworks.net services