ocr-pdf-via-document-ai

Takes a set of jpg files, runs OCR on them via Google Cloud Document AI and outputs

• A plain text file per input image
• The raw docai JSON output
• A HOCR file per input image (can be opened as a standalone HTML file via hocrjs)
• A PDF file with an invisible text layer to make it searchable

Example:

Input Image	Debug Output

Why a cloud service?

Tesseract is the best open-source OCR engine, but sadly the Google Service performs much better and has the following extra features:

• Supports any number of languages mixed together (also outputs per-line language confidence scores)
• Detects and corrects any page orientation
• High recognition accuracy with different fonts and even handwriting
• In theory the option for advanced capabilities such as table extraction / form extraction

Cost

Currently the price is $1.5 per 1000 pages (see here).

Installation and Running

You'll need to set up the following env variables:

• GOOGLE_APPLICATION_CREDENTIALS: (only if you don't have default credentials) path to a json file giving access to Document AI
• API_ENDPOINT: e.g. eu-documentai.googleapis.com
• PROCESSOR_NAME: something like projects/00000000000/locations/eu/processors/fffffffffffff

Then run:

yarn install

yarn run ocr --writePdf out.pdf --writeTxt --input input_dir/*.jpg

The aw document-ai output is always written so if you run it again it will only do API calls for new files.

TODO

• Package as npm package, fix startup time
• Ensure PDF output has all the text in the "correct" order when run through pdftotext (also compare with hocr-pdf)