pdf2oac v6.3.1

pdf2oac

Extract annotations from PDF files and convert them to the Open Annotation Core data model.

Requires libpoppler and a C compiler that supports C++11.

Installation

pdf2oac requires running a patched version of libpoppler that is built from source. The patches allow handling stamp annotations and rendering annotations to images. They can be found in the libpoppler/patches directory.

To patch and build the patched libpoppler, and then build the Node extension, all you need to do is run npm install. However, for this to run successfully will require several dependencies to be installed through your OS's package manager:

• libcairo
• libglib2.0
• libpixman
• libfreetype2
• libpng

Node.js library

Example

const pdf2oac = require('pdf2oac')

pdf2oac('~/Documents/annotated_document.pdf')
  .on('data', triple => {
    console.log(triple);
  })
  .on('close', () => {
    console.log('all done!');
  })

Methods

const pdf2oac = require('pdf2oac')

pdf2oac(pdfFilename, options={})

Returns a ReadableStream that will extract annotations from the given pdf and stream objects with subject, predicate, object, and possibly graph attributes.

Available options (all optional):

• imageDirectory: pdf2oac uses the program pdfimages (packaged with poppler-utils) to extract annotation images. If this option is provided, the given directory will be used to temporarily store the image files produced by pdfimages. If it is omitted, a temporary directory will be created automatically and deleted after completion.

• pdfURI: The URI that will be used as the RDF resource representing the PDF file. Defaults to file://$pdfFilename.

• baseURI: The base URI for all generated triples. Defaults to http://example.org/#.

• graphURI: If provided, the returned stream will emit quads ({ subject, predicate, object, graph }) with the given graph URI rather than triples ({ subject, predicate, object }).

Command line utility

pdf2oac ~/Documents/annotated_document.pdf --format turtle > annotations.ttl

Available options:

• --pdf-uri: Same as pdfURI, above.

• --baseURI: Same as baseURI, above.

• --graphURI: Same as graphURI, above.

• -f, --format: The output format. One of turtle, trig, n-triples, n-quads, or json. Default is trig if graph URI is provided, or turtle if not. json does not return JSON-LD. Rather, it outputs { subject, predicate, object, ?graph } triples/quads.