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OCRODJVU(1) ocrodjvu manual OCRODJVU(1)

NAME

ocrodjvu - OCR for DjVu files

SYNOPSIS

ocrodjvu { -o | --save-bundled} output-djvu-file [option...] djvu-file
ocrodjvu { -i | --save-indirect} index-djvu-file [option...] djvu-file
ocrodjvu --save-script script-file [option...] djvu-file
ocrodjvu --in-place [option...] djvu-file
ocrodjvu --dry-run [option...] djvu-file
ocrodjvu { --version | --help | -h | --list-engines | --list-languages}

DESCRIPTION

ocrodjvu is a wrapper for OCR systems that allows you to perform OCR on DjVu files.
The following OCR engines are supported:
 
•OCRopus[1] (internally, ocrodjvu calls ocroscript's recognize (or rec-tess) command, so that ultimately Tesseract acts as the OCR backend);
 
•Cuneiform for Linux[2].
 
•Ocrad[3].
 
•GOCR[4].
 
•Stand-alone Tesseract[5].
 

OPTIONS

OCR engine options

-e, --engine=engine-id
Use this OCR engine. The default is ‘ocropus’ (OCRopus).
--list-engines
Print list of available OCR engines.

Options controlling output

It is mandatory to use exactly one of the following options:
-o, --save-bundled=output-djvu-file
Save OCR results as a bundled multi-page document into output-djvu-file.
-i, --save-indirect=index-djvu-file
Save OCR results as an indirect multi-page document. Use index-djvu-file as the index file name; put the component files into the same directory. The directory must exist and be writable.
--save-script=script-file
Save a djvused script with OCR results into script-file.
--in-place
Save OCR results in place.
 
(Use this option to retain compatibility with ocrodjvu < 0.2.)
--dry-run
Don't change any files, throw OCR results away.

Text segmentation options

-t lines, --details lines
Record location of every line. Don't record locations of particular words or characters.
 
This is the default for OCRopus 0.2. The option is ineffective with stand-alone Tesseract 2.0.
-t words, --details=words
Record location of every line and every word. Don't record locations of particular characters.
 
This is the default for most OCR engines.
 
This option is ineffective with OCRopus 0.2 and stand-alone Tesseract 2.0.
-t chars, --details=chars
Record location of every line, every word and every character.
 
This option is ineffective with OCRopus 0.2 and stand-alone Tesseract 2.0.
--word-segmentation=simple
Consider each non-empty sequence of non-whitespace characters a single word.
 
This is the default, despite being linguistically incorrect.
--word-segmentation=uax29
Use the Unicode Text Segmentation[6] algorithm to break lines into words.
 
This option breaks assumptions of some DjVu tools that words are separated by spaces, and therefore it is not recommended.

Other options

--clear-text
Remove existing hidden text if present in the pages not selected for OCR.
 
(Use this option to retain compatibility with ocrodjvu < 0.2.)
--ocr-only
Don't save pages that were not processed.
-l, --language=language-id
Set recognition language. language-id is typically an ISO 639-2/T three-letter code.
 
For OCRopus, the default is ‘eng’ (English), unless the tesslanguage environment variable is set. For other OCR engines, the default is always ‘eng’.
--list-languages
Print list of available languages for the currently selected OCR engine.
--render=mask
Render only masks of page images.
 
This is the default.
--render=foreground
Render only foreground layers of page images.
--render=all
Render all layers of page images.
 
This option is necessary to OCR DjVu files with invalid foreground/background separation.
-p, --pages=page-range
Specifies pages to process. page-range is a comma-separated list of sub-ranges. Each sub-range is either a single page (e.g. 17) or a contiguous range of pages (e.g. 37-42). Pages are numbered from 1.
 
The default is to process all pages.
-j, --jobs=n
Start up to n OCR processes.
--version
Output version information and exit.
-h, --help
Display help and exit.

Advanced options

-D, --debug
To ease debugging, don't delete intermediate files.
-X key=value
This option allow to control some details of how ocrodjvu operates.
--on-error=abort
Stop program execution when exception situation (e.g., malformed output from the OCR engine, internal ocrodjvu error, etc.) occurs.
 
This is the default.
--on-error=resume
Attempt to recover from exceptional situations.
 
This option is strongly discouraged.
--html5
Use a HTML5 parser[7], which is more robust but slower than the default parser.

ENVIRONMENT

The following environment variables affects ocrodjvu:
tesslanguage
Recognition language for Tesseract.
 
(Use this variable is deprecated in favor of the --language option.)
TMPDIR
ocrodjvu makes heavy use of temporary files. It will store them in a directory specified by this variable. The default is /tmp.

BUGS

Tesseract 3.00 is affected by a bug [8] making it produce invalid hOCR output in certain circumstances. ocrodjvu does not try recover form this fault (which couldn't be done reliably anyway) unless you pass the -X fix-html=1 option.
When using Tesseract ≥ 3.00, extracting bounding boxes of particular characters (which happens when either --details=chars or --word-segmentation=uax29) is inefficient. This due to limitations of Tesseract command line interface.

SEE ALSO

 
djvu(1), ocroscript(1), tesseract(1), cuneiform(1), ocrad(1), gocr(1)

AUTHOR

Jakub Wilk <jwilk@jwilk.net>
Author.

NOTES

1.
OCRopus
http://ocropus.googlecode.com/
2.
Cuneiform for Linux
http://launchpad.net/cuneiform-linux
3.
Ocrad
http://www.gnu.org/software/ocrad/
4.
GOCR
http://jocr.sourceforge.net/
5.
Tesseract
http://code.google.com/p/tesseract-ocr/
6.
Unicode Text Segmentation
http://unicode.org/reports/tr29/
7.
HTML5 parser
http://www.whatwg.org/specs/web-apps/current-work/#html-parser
8.
http://code.google.com/p/tesseract-ocr/issues/detail?id=376
 
03/10/2012 ocrodjvu 0.7.9