mirror of
https://github.com/tesseract-ocr/tesseract.git
synced 2025-08-06 13:56:47 +08:00
Improve formatting for automatic TOC generation for asciidoc
Shreeshrii
parent
836356ddea
commit
c6fa0386eb
269
FAQ.asciidoc
269
FAQ.asciidoc
@ -5,6 +5,7 @@ ifdef::env-github[]
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:important-caption: :heavy_exclamation_mark:
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:caution-caption: :fire:
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:warning-caption: :warning:
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:sectlinks:
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endif::[]
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= Frequently Asked Questions (Tesseract 4)
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@ -39,16 +40,14 @@ forum.
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toc::[]
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[[how-do-i-get-tesseract-4.0.0]]
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How do I get Tesseract 4.0.0?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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= Tesseract 4.0.0
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== How do I get Tesseract?
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See https://github.com/tesseract-ocr/tesseract/wiki[Tesseract Wiki Home]
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page for details.
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[[which-language-models-are-available-for-tesseract-4.0.0]]
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Which language models are available for Tesseract 4.0.0?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== Which language models are available for Tesseract?
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See Tesseract man page for the list of
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https://github.com/tesseract-ocr/tesseract/blob/master/doc/tesseract.1.asc#languages[languages]
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@ -65,10 +64,7 @@ User contributed language models are linked from
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https://github.com/tesseract-ocr/tesseract/wiki/Data-Files-Contributions[Data
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Files Contributions].
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[[where-are-the-language-models-traineddata-files-for-tesseract-4.0.0-installed]]
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Where are the language models (traineddata files) for Tesseract 4.0.0
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installed?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== Where are the language models (traineddata files) for Tesseract installed?
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The files should be installed in /usr/share/tesseract-ocr/4.00/tessdata
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(on Ubuntu).
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@ -77,9 +73,7 @@ If you get an error message saying eng.traineddata not found, try
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setting `TESSDATA_PREFIX=/usr/share/tesseract-ocr/4.00/tessdata` and all
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will be good.
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[[what-output-formats-can-tesseract-produce]]
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What output formats can Tesseract produce?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== What output formats can Tesseract produce?
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* txt
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* pdf
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@ -111,9 +105,19 @@ merged with an images-only PDF. See
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https://github.com/tesseract-ocr/tesseract/issues/660#issuecomment-385669193[issue
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660] for related discussion and utility for merging the PDFs.
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[[how-do-i-run-tesseract-4.0.0-from-the-command-line]]
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How do I run Tesseract 4.0.0 from the command line?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== What page separators are used in txt output by Tesseract 4.0.0?
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Each page will be terminated by the FF character by default for text
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output.
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Setting `page_separator` to the LF character would restore the old
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behaviour of adding an empty line at the end of each page.
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Setting `page_separator` to an empty string would omit page separators.
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= Running Tesseract
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== How do I run Tesseract 4.0.0 from the command line?
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See
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https://github.com/tesseract-ocr/tesseract/wiki/Command-Line-Usage[Tesseract
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@ -123,9 +127,7 @@ from the command line.
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`tesseract --help` will provide the most recent help information for the
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installed version.
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[[how-to-process-multiple-images-in-a-single-run]]
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How to process multiple images in a single run?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== How to process multiple images in a single run?
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Prepare a text file that has the path to each image:
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@ -139,85 +141,18 @@ Save it, and then give its name as input file to Tesseract.
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`tesseract savedlist output`
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[[what-page-separators-are-used-in-txt-output-by-tesseract-4.0.0]]
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What page separators are used in txt output by Tesseract 4.0.0?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== How to OCR streaming images to pdf using Tesseract?
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Each page will be terminated by the FF character by default for text
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output.
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Let's say you have an amazing but slow multipage scanning device. It
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would be nice to OCR during scanning. In this example, the scanning
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program is sending image filenames to Tesseract as they are produced.
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Tesseract streams a searchable PDF to stdout.
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Setting `page_separator` to the LF character would restore the old
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behaviour of adding an empty line at the end of each page.
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....
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scanimage --batch --batch-print | tesseract -c stream_filelist=true - - pdf > output.pdf
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....
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Setting `page_separator` to an empty string would omit page separators.
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[[how-do-i-use-tesseract-4.0.0-using-the-api]]
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How do I use Tesseract 4.0.0 using the API?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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See https://github.com/tesseract-ocr/tesseract/wiki/APIExample[Tesseract
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Wiki API examples] page for sample programs for using the API.
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[[how-do-i-improve-ocr-results]]
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How do I improve OCR results?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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You should note that in many cases, in order to get better OCR results,
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you'll need to
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https://github.com/tesseract-ocr/tesseract/wiki/ImproveQuality[improve
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the quality] of the input image you are giving Tesseract.
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[[can-i-increase-speed-of-ocr]]
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Can I increase speed of OCR?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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If you are running Tesseract 4, you can use the "fast" integer models.
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Tesseract 4 also uses up to four CPU threads while processing a page, so
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it will be faster than Tesseract 3 for a single page.
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If your computer has only two CPU cores, then running four threads will
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slow down things significantly and it would be better to use a single
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thread or maybe a maximum of two threads! Using a single thread
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eliminates the computation overhead of multithreading and is also the
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best solution for processing lots of images by running one Tesseract
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process per CPU core.
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Set the maximum number of threads using the environment variable
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`OMP_THREAD_LIMIT`.
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To disable multithreading, use `OMP_THREAD_LIMIT=1`.
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[[how-do-i-train-tesseract-4.0.0-lstm-engine]]
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How do I train Tesseract 4.0.0 LSTM Engine?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Tesseract can be trained to recognize other languages or finetune
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existing language models. See
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https://github.com/tesseract-ocr/tesseract/wiki/TrainingTesseract-4.00[Tesseract
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Wiki Training Tesseract 4.00] page for information on training the LSTM
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engine.
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Please note that currently LSTM training is only supported using
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synthetic images created using a UTF-8 training text and unicode fonts
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to render the text.
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[[there-are-inconsistent-results-from-tesseract-when-the-same-tessbaseapi-object-is-used-for-decoding-multiple-images]]
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There are inconsistent results from tesseract when the same TessBaseAPI
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object is used for decoding multiple images
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Try to turn off the adaptive classifier by setting the config variable
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`classify_enable_learning` to `0`, or to clear the adaptive data with
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the method `ClearAdaptiveClassifier()`.
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See also the discussion on the
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https://groups.google.com/d/topic/tesseract-ocr/ByGJhocI9qQ[tesseract
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forum]
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[[how-can-i-make-the-error-messages-go-to-tesseract.log-instead-of-stderr]]
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How can I make the error messages go to tesseract.log instead of stderr?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== How can I make the error messages go to tesseract.log instead of stderr?
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To restore the old behaviour of writing to tesseract.log instead of
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writing to the console window, you need a text file that contains this:
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@ -227,9 +162,7 @@ debug_file tesseract.log
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call the file 'logfile' and put it in tessdata/configs/ Then add logfile
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to the end of your command line.
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[[how-can-i-suppress-tesseract-info-line]]
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How can I suppress tesseract info line?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== How can I suppress tesseract info line?
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See
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https://web.archive.org/web/*/http://code.google.com/p/tesseract-ocr/issues/detail?id=579[issue
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@ -249,67 +182,48 @@ tesseract phototest.tif phototest quiet
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*Warning:* Both options will cause you to not see the error message if
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there is one.
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[[how-do-i-produce-searchable-pdf-output]]
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How do I produce searchable PDF output?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== How do I use Tesseract 4.0.0 using the API?
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Searchable PDF output is a standard feature as of Tesseract version
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3.03. Use the `pdf` config file like this:
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See https://github.com/tesseract-ocr/tesseract/wiki/APIExample[Tesseract
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Wiki API examples] page for sample programs for using the API.
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....
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tesseract phototest.tif phototest pdf
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....
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== There are inconsistent results from tesseract when the same TessBaseAPI object is used for decoding multiple images.
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[[the-searchable-pdf-seems-to-contain-only-spaces-or-spaces-between-the-letters-of-words]]
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The searchable PDF seems to contain only spaces or spaces between the
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letters of words
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Try to turn off the adaptive classifier by setting the config variable
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`classify_enable_learning` to `0`, or to clear the adaptive data with
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the method `ClearAdaptiveClassifier()`.
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There may be nothing wrong with the PDF itself, but its hidden,
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searchable text layer may be not understood by your PDF reader. For
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example, Preview.app in Mac OS X is well known for having problems like
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this, and might "see" only spaces and no text. Try using Adobe Acrobat
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Reader instead.
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See also the discussion on the
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https://groups.google.com/d/topic/tesseract-ocr/ByGJhocI9qQ[tesseract
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forum]
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[[how-to-do-streaming-of-images-to-pdf-using-tesseract]]
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How to do streaming of images to pdf using Tesseract?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== How do I improve OCR results?
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Let's say you have an amazing but slow multipage scanning device. It
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would be nice to OCR during scanning. In this example, the scanning
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program is sending image filenames to Tesseract as they are produced.
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Tesseract streams a searchable PDF to stdout.
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You should note that in many cases, in order to get better OCR results,
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you'll need to
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https://github.com/tesseract-ocr/tesseract/wiki/ImproveQuality[improve
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the quality] of the input image you are giving Tesseract.
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....
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scanimage --batch --batch-print | tesseract -c stream_filelist=true - - pdf > output.pdf
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....
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== Can I increase speed of OCR?
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[[can-i-use-tesseract-for-handwriting-recognition]]
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Can I use Tesseract for handwriting recognition?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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If you are running Tesseract 4, you can use the "fast" integer models.
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You can, but it won't work very well, as Tesseract is designed for
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printed text. Take a look at the http://lipitk.sourceforge.net/[Lipi
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Toolkit] project instead.
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Tesseract 4 also uses up to four CPU threads while processing a page, so
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it will be faster than Tesseract 3 for a single page.
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[[can-i-use-tesseract-for-barcode-recognition]]
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Can I use tesseract for barcode recognition?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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If your computer has only two CPU cores, then running four threads will
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slow down things significantly and it would be better to use a single
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thread or maybe a maximum of two threads! Using a single thread
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eliminates the computation overhead of multithreading and is also the
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best solution for processing lots of images by running one Tesseract
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process per CPU core.
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No. Tesseract is for text recognition.
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Set the maximum number of threads using the environment variable
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`OMP_THREAD_LIMIT`.
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[[where-is-the-documentation]]
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Where is the documentation?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To disable multithreading, use `OMP_THREAD_LIMIT=1`.
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You're looking at it. If things aren't clear, search on the
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http://groups.google.com/group/tesseract-ocr/[Tesseract Google Group] or
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ask us there. If you want to help us write more, please do, and post it
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to the group!
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[[how-can-i-try-the-next-version]]
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How can I try the next version?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== How can I try the next version?
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Periodically stable versions go to the downloads page. Between releases,
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and in particular, just before a new release, the latest code is
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@ -318,11 +232,9 @@ https://github.com/tesseract-ocr/tesseract.git where you can check it
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out either by command line, or by following the link to the howto on
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using various client programs and plugins.
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[[how-do-i-compare-different-versions-of-tesseract]]
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How do I compare different versions of Tesseract
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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== How do I compare different versions of Tesseract
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If you want to have several version of tesseract (e.g. you want to
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If you want to have several versions of tesseract (e.g. you want to
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compare OCR result) I would suggest you to compile them from source
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(e.g. in /usr/src) and not install them. If you want to test particular
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version you can run it this way:
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@ -336,9 +248,60 @@ version you can run it this way:
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will take care that correct shared library is used (without
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installation...).
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[[my-question-isnt-in-here]]
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My question isn't in here!
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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= Training
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== How do I train Tesseract 4.0.0 LSTM Engine?
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Tesseract can be trained to recognize other languages or finetune
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existing language models. See
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https://github.com/tesseract-ocr/tesseract/wiki/TrainingTesseract-4.00[Tesseract
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Wiki Training Tesseract 4.00] page for information on training the LSTM
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engine.
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Please note that currently LSTM training is only supported using
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synthetic images created using a UTF-8 training text and unicode fonts
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to render the text.
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= pdf
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== How do I produce searchable PDF output?
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Searchable PDF output is a standard feature as of Tesseract version
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3.03. Use the `pdf` config file like this:
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....
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tesseract phototest.tif phototest pdf
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....
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== The searchable PDF seems to contain only spaces or spaces between the letters of words.
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There may be nothing wrong with the PDF itself, but its hidden,
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searchable text layer may be not understood by your PDF reader. For
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example, Preview.app in Mac OS X is well known for having problems like
|
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this, and might "see" only spaces and no text. Try using Adobe Acrobat
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Reader instead.
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= Miscellaneous
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== Can I use Tesseract for handwriting recognition?
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You can, but it won't work very well, as Tesseract is designed for
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printed text. Look for projects focussed on handwriting recognition.
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== Can I use tesseract for barcode recognition?
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No. Tesseract is for text recognition.
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== Where is the documentation?
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You're looking at it. If things aren't clear, search on the
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http://groups.google.com/group/tesseract-ocr/[Tesseract Google Group] or
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ask us there. If you want to help us write more, please do, and post it
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to the group!
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== My question isn't in here!
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Try searching the forum: http://groups.google.com/group/tesseract-ocr as
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well as open and closed issues on GitHub:
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Reference in New Issue
Block a user