pmOCR (poor man's OCR tool)
A multicore batch & service wrapper script for Tesseract v3/v4/v5 (https://github.com/tesseract-ocr/) or ABBYY CLI OCR 11 FOR LINUX based on Finereader Engine 11 optical character recognition (www.ocr4linux.com).
Conversions support tiff/jpg/png/pdf/bmp to PDF, TXT and CSV (also DOCX and XSLX for Abbyy OCR). It can actually support any other format that your OCR engine can handle.
This wrapper can work both in batch and service mode.
In batch mode, it's used as commandline tool for processing multiple files at once, being able to output one or more formats.
In service mode, it will monitor directories and launch OCR conversions as soon as new files get into the directories. Since v1.8.0, it can also monitor NFS / SMB mountpoints with new integrated inotifywait emulation poller.
pmOCR has the following options:
- Include current date into the output filename
- Ignore already OCRed PDF files based on font detection and / or file suffix
- Delete or move input file after successful conversion
Install it
$ git clone https://github.com/deajan/pmOCR
$ cd pmOCR
$ ./install.sh
You will need pdffonts util (from poppler-utils package). Optionally, you can install inotifywait (from inotify-tools package).
If you are using tesseract OCR, please install tesseract-osd and tesseract-[your language] (sometimes called tesseract-ocr-osd). You will also need ImageMagick in order to be able to transform bitmap PDF documents to indexed PDFs.
Batch mode
Use pmocr to batch process all files in a given directory and its subdirectories.
Use --help for command line usage.
Example:
$ pmocr.sh --batch --target=pdf --skip-txt-pdf --delete-input /some/path
$ pmocr.sh --batch --target=pdf --target=csv --suffix=processed /some/path
If pmOCR wasn't installed, you may run it directly with a configuration file like:
$ ./pmocr.sh --config=./default.conf --batch -p /some/path
OCR Configuration
pmOCR uses a default config stored in /etc/pmocr/default.conf You may change it's contents or clone it and have pmOCR use an alternative configuration with:
$ pmocr.sh --config=/etc/pmocr/myConfig.conf --batch --target=csv /some/path
Service mode
Service mode monitors directories and their subdirectories and launched an OCR conversion whenever a new file is written. Keep in mind that only file creations are monitored. File moves aren't.
pmocr is written to monitor up to 5 directories, each producing a different target format (PDF, DOCX, XLSX, TXT & CSV). Comment out a folder to disable it's monitoring.
There's also an option to avoid passing PDFs to the OCR engine that already contain text.
After installation, please configure /etc/pmocr/default.conf in order to monitor the directories you need, and adjust your specific options.
Launch service (initV style) service pmocr-srv start
Launch service (systemd style) systemctl start [email protected]
Check service state (initV style) service pmocr-srv status
Check service state (systemd style) systemctl status [email protected]
Multiple service instances
In order to monitor multiple directories with different OCR settings, you need to duplicate /etc/pmocr/default.conf configuration file. When launching pmOCR service with initV, each config file will create an instance. With systemD, you have to launch a service for each config file. Example for configs /etc/pmocr/default.conf and /etc/pmocr/other.conf
$ systemctl start [email protected]
$ systemctl start [email protected]
Support for OCR engines
Has been tested so far with:
- ABBYY FineReader OCR Engine 11 CLI for Linux releases R2 (v 11.1.6.562411), R3 (v 11.1.9.622165) and R6 (v 11.1.14.707470)
- Tesseract-ocr 3.0.4
- Tesseract-ocr 4.0.0 and 4.0.12
- Tesseract-ocr 5.0.0 and 5.0.1
Tesseract mode also uses ghostscript to convert PDF files to an intermediary TIFF format in order to process them.
It should virtually work with any engine as long as you adjust the parameters.
Parameters include any arguments to pass to the OCR program depending on the target format.
Support for OCR Preprocessors
ABBYY has in integrated preprocessor in order to enhance recognition qualitiy whereas Tesseract relies on external tools. pmOCR can use a preprocessor like ImageMagick to deskew / clear noise / render white background and remove black borders. ImageMagick preprocessor is configured, and enabled by default to be used with Tesseract.
Tesseract caveats
When no OSD / language data is installed, tesseract will still process documents, but the quality may suffer. While pmocr will warn you about this, the conversion still happens. Please make sure to install all necessary addons for tesseract.
Troubleshooting
Please check /var/log/pmocr.log or ./pmocr.log file for errors.
Filenames containing special characters should work, nevertheless, if your file doesn't get converted, try to rename it and copy it again to the monitored directory or batch process it again.
By default, failing to prevent files will add a prefix '_OCR_ERR' + date to the filename. In order to reprocess those files, the prefix has to be removed with the following command
$ find /monitor/path -iname "*_OCR_ERR.*" -print0 | xargs -0 -I {} sh -c 'export file="{}"; mv "$file" "${file//_OCR_ERR/}"'
If using tesseract to create searchable PDF files, please make sure to have version 3.03 or better installed.