PDFtoOCR does OCR processing on PDF documents. The text from OCR is used in the search results.
The PDFtoOCR product processes text in PDF documents using OCR. This is needed when text cannot be extracted from a (scanned) PDF. PDFtoOCR uses content rules to schedule the OCR processing. The processing cannot be done one the fly, for example with a custom TextIndexNG plugin. Processing large PDF documents using OCR is a time consuming task.
On the operating system
PDF to Text uses three tools that are available for under Linux. The cooperation with the tools is only tested in Debian. But it the will probably work in in other nix enviroments.
Install requirements, PDF to OCR uses the following programs:
- pdftotext, checks if OCR processing is necessary
- ghostscript, converts the pdf documents to tiff images
- tesseract, does the OCR processing (make sure you’ve got all language packs!*)
On the Plone site
Add a content rule
- Event trigger: Object modified
- Condition: Content type is file
- Actions: Store OCR output from a PDF in searchable text
Assign content rule to a Plone site or a folder
Install cron4plone and add the following cronjob: portal/@@do_pdf_ocr_index
Each time a file is added or modified the unique id (uid) of the file is added to a queue. This queue is persistent and has two functions, for indexing en reindexing. The indexing function uses the queue to process the documents. When reindexing is used all files in the queue history are processed.
If the text from a PDF document is extracted using pdftotext no OCR is done. Else the OCR extracts the text and stores it the content type file. The ATFile is patched with an extra field to accommodate the extracted text and the language of the PDF.
- @@do_pdf_ocr_index - indexes documents in the queue
- @@do_pdf_ocr_reindex - reindexes all pdf documents in the Plone site
- @@pdf_ocr_status - Show the queue and a history 10 documents
- When using Plone 3.x pin down PDFtoOCR::
- [versions] ... Products.PDFtoOCR = 1.0dev
- Make sure you don’t got empty language files in /usr/local/share/tessdata/
Maybe a good alternative in the future, uses tessract but hard to setup and still too much beta: http://sites.google.com/site/ocropus/
1.0 - Unreleased
- Initial release