问题
Has anybody attempted to extract text from a PDF using an OCR library and Java? What did you find to be the most reliable library for text extraction. Most of the approaches I've seen (tesseract, GOCR) are C libraries that would require some JNI code to be written.
I'm familiar with pdfbox, which is now an Apache incubator project at version 0.8.x, but it's text extraction isn't always accurate. I'm looking for an alternative approach that is somewhat more reliable.
I've not tried Asprise JavaPDF yet, in the process of trying that, but wanted to know more about the OCR approach (if it's possible).
Any help would be appreciated.
回答1:
If you have a text-based PDF, I'd strongly recommend PDFTextStream. It's not free, but licensing is reasonable, and it is much much better than PDFBox. PDFBox chokes on many PDF files which are generated by newer tools, and is not too consistent about PDFs it can handle. PDFTextStream handles any PDF I throw at it, including PDFs with embedded PNG images, which PDFBox can not do.
If you heckle the PDFTextStream folks to add OCR, they may listen up.
回答2:
We use ABBYY FineReader Engine 11. They have java wrapper.
Pros:
- It works great with all the languages (English, Russian, Uzbek etc) and doing real OCR (even if you have pdf without OCR they perform rendering at first and OCRing).
Cons:
It costs. You have to buy developer license and end-user license.
And it is EXTREMELY slow.
回答3:
If you want to extract OCR from text based PDF you may have to convert it to an image first.
回答4:
You can use Java wrappers of Tesseract - tesjeract or Tess4J - to perform OCR. However, for PDF, you'll need to convert to image (PNG or TIFF) first before feeding it to the OCR engine.
VietOCR calls Tesseract executable to perform the text extraction. It uses GhostScript to do PDF-to-image conversion.
来源：https://stackoverflow.com/questions/778145/pdf-text-extraction-approach-using-ocr