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Mac Installation Instructions
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brew install tesseract
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tesseract-lang
Issues with Installing via Brew
If you have trouble installing via Brew, some options to try:
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, you can
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try
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installing Tesseract from source.
Tesseract won't work with TIFF files
If you are having trouble getting Tesseract to work with TIFF files, read this link. Summary:
- uninstall tesseract:
brew uninstall tesseract
- 2. uninstall leptonica:
brew uninstall leptonica
- 3. install leptonica with tiff support:
brew install leptonica --with-libtiff
4. - install tesseract:
brew install tesseract --with-all-languages --with-serial-num-packtesseract-lang
Installing Tesseract on RHEL
- Add "epel" to your yum repositories if it isn't already installed
1a.wget https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
(or appropriate version)
1b.rpm -Uvh epel-release-latest-7.noarch.rpm
2.yum install tesseract
3. To add language packs, see what's availableyum search tesseract
then, e.g.yum install tesseract-langpack-ara
Installing Tesseract on Ubuntu
sudo apt-get update
- 2.
sudo apt-get install tesseract-ocr
- 3. To add language packs, see what's available then, e.g.
sudo apt-get install tesseract-ocr-fra
Installing Tesseract on Windows
See UB-Mannheim.
Optimizing
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Tesseract
There's some advice on the Tesseract github issues + wiki on ways to speed it up, eg #263 and #1171 and this wiki page.
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Overriding Default Configuration
When using the OCR Parser Tika will use the following default settings:
- Tesseract installation path = ""
- Language dictionary = "eng"
- Page Segmentation Mode = "1"
- Minmum file size = 0
- Maximum file size = 2147483647
- Timeout = 120
To changes these settings you can either modify the existing TesseractOCRConfig.properties file in tika-parser/src/main/resources/org/apache/tika/parser/ocr, or overriding it by creating your own and placing it in the package org/apache/tika/parser/ocr on your classpath.
It is worth noting that doing this when using one of the executable JARs, either the tika-app or tika-server JARs, will require you to execute them without using the -jar command. For example, something like the following for the tika-app or tika-server, respectively:
java -cp /path/to/your/classpath:/path/to/tika-app-X.X.jar org.apache.tika.cli.TikaCLI
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In Tika 2.x, users can modify configurations via a tika-config.xml
. With the exceptions of the paths, we document the defaults in the following:
Code Block | ||||
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| ||||
<properties>
<parsers>
<parser class="org.apache.tika.parser.DefaultParser">
<!-- this is not formally necessary, but prevents loading of unnecessary parser -->
<parser-exclude class="org.apache.tika.parser.ocr.TesseractOCRParser"/>
</parser>
<parser class="org.apache.tika.parser.ocr.TesseractOCRParser">
<params>
<!-- these are the defaults; you only need to specify the ones you want
to modify -->
<param name="applyRotation" type="bool">false</param>
<param name="colorSpace" type="string">gray</param>
<param name="density" type="int">300</param>
<param name="depth" type="int">4</param>
<param name="enableImagePreprocessing" type="bool">false</param>
<param name="filter" type="string">triangle</param>
<param name="imageMagickPath" type="string">/my/custom/imageMagicPath</param>
<param name="language" type="string">eng</param>
<param name="maxFileSizeToOcr" type="long">2147483647</param>
<param name="minFileSizeToOcr" type="long">0</param>
<param name="pageSegMode" type="string">1</param>
<param name="pageSeparator" type="string"></param>
<param name="preserveInterwordSpacing" type="bool">false</param>
<param name="resize" type="int">200</param>
<param name="skipOcr" type="bool">false</param>
<param name="tessdataPath" type="string">/my/custom/data</param>
<param name="tesseractPath" type="string">/my/custom/path</param>
<param name="timeoutSeconds" type="int">120</param>
</params>
</parser>
</parsers>
</properties> |
OCR and PDFs
See also PDFParser notes for more details on options for performing OCR on PDFs.
Note: With Tika server 1.x, the PDFConfig is generated for each document, so any configurations that you may specify in the tika-config.xml file that you pass to the tika-server on startup are overwritten. This behavior is changed in Tika 2.x, where the PDFConfig remembers settings from tika-config.xml and will only temporarily update custom configs sent via headers.
To go with option 1 for OCR'ing PDFs (run OCR against inline images), you need to specify configurations for the PDFParser like so:
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To go with option 2 (render each page and then run OCR on that rendered image), you need to specify the ocr strategy:curl -T testOCR.pdf http://localhost:9998/tika --header "X-Tika-PDFOcrStrategy: ocr_only"
Note: These two options are independent. If you set extractInlineImages
to true and select an OcrStrategy
that includes OCR on the rendered page, Tika will run OCR on the extracted inline images and the rendered page.
Disable
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OCR in Tika
Anchor | ||||
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Tika's OCR will trigger on images embedded within, say, office documents in addition to images you upload directly. Because OCR slows down Tika, you might want to disable it if you don't need the results. You can disable OCR by simply uninstalling tesseract, but if that's not an option, here is a tika.xml config file that disables OCR:
No Format |
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<?xml version="1.0" encoding="UTF-8"?> <properties> <parsers> <parser class="org.apache.tika.parser.DefaultParser"> <parser-exclude class="org.apache.tika.parser.ocr.TesseractOCRParser"/> </parser> </parsers> </properties> |
In Tika 2.x, you can selectively turn off OCR per parse programmatically by setting skipOcr
on a TesseractOCRConfig
. This will only affect that one call to parse.
No Format |
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TesseractOCRConfig config = new TesseractOCRConfig();
config.setSkipOcr(true);
ParseContext context = new ParseContext();
context.set(TesseractOCRConfig.class, config);
Parser parser = new AutoDetectParser();
parser.parse(inputStream, handler, metadata, context); |
In Tika 2.x, with tika-server
, add this header to skip OCR per request: X-Tika-OCRskipOcr: true
Optional Dependencies
Tika will run preprocessing of images (rotation detection and image normalizing with ImageMagick) before sending the image to tesseract if the user has included dependencies (listed below) and if the user opts to include these preprocessing steps.
To identify rotation
python must be installed with scikit-image and numpy
pip3 install numpy
pip3 install scikit-image
(As of January 5, 2021, there's a bug in the most recent numpy for Windows, specify 1.19.3: pip3 install numpy==1.19.3
)
In Tika 2.0, python3
must be installed and callable as python3
.
Install ImageMagick
See: https://imagemagick.org/script/download.php
iOS: brew install imagemagick
Ubuntu: sudo apt install imagemagick
Windows: download the binary installer from the above page, e.g. https://imagemagick.org/download/binaries/ImageMagick-7.0.10-55-Q16-HDRI-x64-dll.exe
TODO: document how to configure these options in Tika