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397 lines
10 KiB
Plaintext
397 lines
10 KiB
Plaintext
TESSERACT(1)
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============
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:doctype: manpage
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NAME
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----
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tesseract - command-line OCR engine
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SYNOPSIS
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--------
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*tesseract* 'imagename'|'stdin' 'outputbase'|'stdout' [options...] [configfile...]
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DESCRIPTION
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-----------
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tesseract(1) is a commercial quality OCR engine originally developed at HP
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between 1985 and 1995. In 1995, this engine was among the top 3 evaluated by
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UNLV. It was open-sourced by HP and UNLV in 2005, and has been developed
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at Google since then.
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IN/OUT ARGUMENTS
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----------------
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'imagename'::
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The name of the input image. Most image file formats (anything
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readable by Leptonica) are supported.
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'stdin'::
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Instruction to read data from standard input
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'outputbase'::
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The basename of the output file (to which the appropriate extension
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will be appended). By default the output will be named 'outbase.txt'.
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'stdout'::
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Instruction to sent output data to standard output
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OPTIONS
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-------
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'--tessdata-dir /path'::
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Specify the location of tessdata path
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'--user-words /path/to/file'::
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Specify the location of user words file
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'--user-patterns /path/to/file'::
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Specify the location of user patterns file
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'-c configvar=value'::
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Set value for control parameter. Multiple -c arguments are allowed.
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'-l lang'::
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The language to use. If none is specified, English is assumed.
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Multiple languages may be specified, separated by plus characters.
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Tesseract uses 3-character ISO 639-2 language codes. (See LANGUAGES)
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'--psm N'::
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Set Tesseract to only run a subset of layout analysis and assume
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a certain form of image. The options for *N* are:
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0 = Orientation and script detection (OSD) only.
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1 = Automatic page segmentation with OSD.
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2 = Automatic page segmentation, but no OSD, or OCR.
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3 = Fully automatic page segmentation, but no OSD. (Default)
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4 = Assume a single column of text of variable sizes.
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5 = Assume a single uniform block of vertically aligned text.
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6 = Assume a single uniform block of text.
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7 = Treat the image as a single text line.
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8 = Treat the image as a single word.
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9 = Treat the image as a single word in a circle.
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10 = Treat the image as a single character.
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'--oem N'::
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Specify OCR Engine mode. The options for *N* are:
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0 = Original Tesseract only.
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1 = Neural nets LSTM only.
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2 = Tesseract + LSTM.
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3 = Default, based on what is available.
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'configfile'::
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The name of a config to use. A config is a plaintext file which
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contains a list of variables and their values, one per line, with a
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space separating variable from value. Interesting config files
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include: +
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* hocr - Output in hOCR format instead of as a text file.
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* pdf - Output in pdf instead of a text file.
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*Nota Bene:* The options '-l lang' and '--psm N' must occur
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before any 'configfile'.
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SINGLE OPTIONS
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--------------
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'-h, --help'::
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Show help message.
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'--help-psm'::
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Show page segmentation modes.
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'--help-oem'::
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Show OCR Engine modes.
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'-v, --version'::
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Returns the current version of the tesseract(1) executable.
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'--list-langs'::
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List available languages for tesseract engine. Can be used with --tessdata-dir.
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'--print-parameters'::
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Print tesseract parameters.
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LANGUAGES
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---------
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The currently available traineddata files for tesseract 4.0
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for the following languages are in
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(in https://github.com/tesseract-ocr/tessdata_fast):
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*afr* (Afrikaans),
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*amh* (Amharic),
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*ara* (Arabic),
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*asm* (Assamese),
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*aze* (Azerbaijani),
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*aze_cyrl* (Azerbaijani - Cyrilic),
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*bel* (Belarusian),
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*ben* (Bengali),
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*bod* (Tibetan),
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*bos* (Bosnian),
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*bre* (Breton),
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*bul* (Bulgarian),
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*cat* (Catalan; Valencian),
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*ceb* (Cebuano),
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*ces* (Czech),
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*chi_sim* (Chinese - Simplified),
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*chi_tra* (Chinese - Traditional),
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*chr* (Cherokee),
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*cym* (Welsh),
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*dan* (Danish),
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*deu* (German),
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*dzo* (Dzongkha),
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*ell* (Greek, Modern (1453-)),
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*eng* (English),
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*enm* (English, Middle (1100-1500)),
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*epo* (Esperanto),
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*equ* (Math / equation detection module),
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*est* (Estonian),
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*eus* (Basque),
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*fas* (Persian),
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*fin* (Finnish),
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*fra* (French),
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*frk* (Frankish),
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*frm* (French, Middle (ca.1400-1600)),
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*gle* (Irish),
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*glg* (Galician),
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*grc* (Greek, Ancient (to 1453)),
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*guj* (Gujarati),
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*hat* (Haitian; Haitian Creole),
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*heb* (Hebrew),
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*hin* (Hindi),
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*hrv* (Croatian),
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*hun* (Hungarian),
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*iku* (Inuktitut),
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*ind* (Indonesian),
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*isl* (Icelandic),
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*ita* (Italian),
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*ita_old* (Italian - Old),
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*jav* (Javanese),
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*jpn* (Japanese),
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*kan* (Kannada),
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*kat* (Georgian),
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*kat_old* (Georgian - Old),
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*kaz* (Kazakh),
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*khm* (Central Khmer),
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*kir* (Kirghiz; Kyrgyz),
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*kor* (Korean),
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*kor_vert* (Korean (vertical)),
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*kur* (Kurdish),
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*kur_ara* (Kurdish (Arabic)),
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*lao* (Lao),
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*lat* (Latin),
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*lav* (Latvian),
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*lit* (Lithuanian),
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*ltz* (Luxembourgish),
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*mal* (Malayalam),
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*mar* (Marathi),
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*mkd* (Macedonian),
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*mlt* (Maltese),
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*mon* (Mongolian),
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*mri* (Maori),
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*msa* (Malay),
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*mya* (Burmese),
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*nep* (Nepali),
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*nld* (Dutch; Flemish),
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*nor* (Norwegian),
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*oci* (Occitan (post 1500)),
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*ori* (Oriya),
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*osd* (Orientation and script detection module),
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*pan* (Panjabi; Punjabi),
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*pol* (Polish),
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*por* (Portuguese),
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*pus* (Pushto; Pashto),
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*que* (Quechua),
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*ron* (Romanian; Moldavian; Moldovan),
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*rus* (Russian),
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*san* (Sanskrit),
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*sin* (Sinhala; Sinhalese),
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*slk* (Slovak),
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*slv* (Slovenian),
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*snd* (Sindhi),
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*spa* (Spanish; Castilian),
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*spa_old* (Spanish; Castilian - Old),
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*sqi* (Albanian),
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*srp* (Serbian),
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*srp_latn* (Serbian - Latin),
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*sun* (Sundanese),
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*swa* (Swahili),
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*swe* (Swedish),
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*syr* (Syriac),
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*tam* (Tamil),
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*tat* (Tatar),
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*tel* (Telugu),
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*tgk* (Tajik),
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*tgl* (Tagalog),
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*tha* (Thai),
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*tir* (Tigrinya),
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*ton* (Tonga),
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*tur* (Turkish),
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*uig* (Uighur; Uyghur),
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*ukr* (Ukrainian),
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*urd* (Urdu),
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*uzb* (Uzbek),
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*uzb_cyrl* (Uzbek - Cyrilic),
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*vie* (Vietnamese),
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*yid* (Yiddish),
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*yor* (Yoruba)
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To use a non-standard language pack named *foo.traineddata*, set the
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*TESSDATA_PREFIX* environment variable so the file can be found at
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*TESSDATA_PREFIX*/tessdata/*foo*.traineddata and give Tesseract the
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argument '-l foo'.
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SCRIPTS
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-------
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The traineddata files for the following scripts for tesseract 4.0
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are also in https://github.com/tesseract-ocr/tessdata_fast.
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In most cases, each of these contains all the languages that use that script PLUS English.
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So it is possible to recognize a language that has not been specifically trained for
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by using traineddata for the script it is written in.
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Arabic,
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Armenian,
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Bengali,
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Canadian Aboriginal,
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Cherokee,
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Cyrillic,
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Devanagari,
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Ethiopic,
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Fraktur,
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Georgian,
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Greek,
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Gujarati,
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Gurmukhi,
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Han - Simplified,
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Han - Simplified (vertical),
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Han - Traditional,
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Han - Traditional (vertical),
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Hangul,
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Hangul (vertical),
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Hebrew,
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Japanese,
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Japanese (vertical),
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Kannada,
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Khmer,
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Lao,
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Latin,
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Malayalam,
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Myanmar,
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Oriya (Odia),
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Sinhala,
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Syriac,
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Tamil,
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Telugu,
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Thaana,
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Thai,
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Tibetan,
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Vietnamese.
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CONFIG FILES AND AUGMENTING WITH USER DATA
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------------------------------------------
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Tesseract config files consist of lines with variable-value pairs (space
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separated). The variables are documented as flags in the source code like
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the following one in tesseractclass.h:
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STRING_VAR_H(tessedit_char_blacklist, "",
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"Blacklist of chars not to recognize");
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These variables may enable or disable various features of the engine, and
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may cause it to load (or not load) various data. For instance, let's suppose
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you want to OCR in English, but suppress the normal dictionary and load an
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alternative word list and an alternative list of patterns -- these two files
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are the most commonly used extra data files.
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If your language pack is in /path/to/eng.traineddata and the hocr config
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is in /path/to/configs/hocr then create three new files:
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/path/to/eng.user-words:
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[verse]
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the
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quick
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brown
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fox
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jumped
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/path/to/eng.user-patterns:
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[verse]
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1-\d\d\d-GOOG-411
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www.\n\\\*.com
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/path/to/configs/bazaar:
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[verse]
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load_system_dawg F
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load_freq_dawg F
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user_words_suffix user-words
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user_patterns_suffix user-patterns
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Now, if you pass the word 'bazaar' as a trailing command line parameter
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to Tesseract, Tesseract will not bother loading the system dictionary nor
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the dictionary of frequent words and will load and use the eng.user-words
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and eng.user-patterns files you provided. The former is a simple word list,
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one per line. The format of the latter is documented in dict/trie.h
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on read_pattern_list().
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HISTORY
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-------
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The engine was developed at Hewlett Packard Laboratories Bristol and at
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Hewlett Packard Co, Greeley Colorado between 1985 and 1994, with some more
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changes made in 1996 to port to Windows, and some $$C++$$izing in 1998. A
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lot of the code was written in C, and then some more was written in $$C++$$.
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The $$C++$$ code makes heavy use of a list system using macros. This predates
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stl, was portable before stl, and is more efficient than stl lists, but has
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the big negative that if you do get a segmentation violation, it is hard to
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debug.
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Version 2.00 brought Unicode (UTF-8) support, six languages, and the ability
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to train Tesseract.
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Tesseract was included in UNLV's Fourth Annual Test of OCR Accuracy.
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See <https://github.com/tesseract-ocr/docs/blob/master/AT-1995.pdf>. With Tesseract 2.00,
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scripts are now included to allow anyone to reproduce some of these tests.
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See <https://github.com/tesseract-ocr/tesseract/wiki/TestingTesseract> for more
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details.
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Tesseract 3.00 adds a number of new languages, including Chinese, Japanese,
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and Korean. It also introduces a new, single-file based system of managing
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language data.
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Tesseract 3.02 adds BiDirectional text support, the ability to recognize
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multiple languages in a single image, and improved layout analysis.
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For further details, see the file ReleaseNotes included with the distribution.
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RESOURCES
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---------
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Main web site: <https://github.com/tesseract-ocr> +
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Information on training: <https://github.com/tesseract-ocr/tesseract/wiki/TrainingTesseract>
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SEE ALSO
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--------
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ambiguous_words(1), cntraining(1), combine_tessdata(1), dawg2wordlist(1),
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shape_training(1), mftraining(1), unicharambigs(5), unicharset(5),
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unicharset_extractor(1), wordlist2dawg(1)
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AUTHOR
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------
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Tesseract development was led at Hewlett-Packard and Google by Ray Smith.
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The development team has included:
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Ahmad Abdulkader, Chris Newton, Dan Johnson, Dar-Shyang Lee, David Eger,
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Eric Wiseblatt, Faisal Shafait, Hiroshi Takenaka, Joe Liu, Joern Wanke,
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Mark Seaman, Mickey Namiki, Nicholas Beato, Oded Fuhrmann, Phil Cheatle,
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Pingping Xiu, Pong Eksombatchai (Chantat), Ranjith Unnikrishnan, Raquel
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Romano, Ray Smith, Rika Antonova, Robert Moss, Samuel Charron, Sheelagh
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Lloyd, Shobhit Saxena, and Thomas Kielbus.
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COPYING
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-------
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Licensed under the Apache License, Version 2.0
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