xmp_parser.py

from collections import defaultdict
from xml.etree import ElementTree as ET

RDF_NS = '{http://www.w3.org/1999/02/22-rdf-syntax-ns#}'
XML_NS = '{http://www.w3.org/XML/1998/namespace}'
NS_MAP = {
    'http://www.w3.org/1999/02/22-rdf-syntax-ns#': 'rdf',
    'http://purl.org/dc/elements/1.1/': 'dc',
    'http://ns.adobe.com/xap/1.0/': 'xap',
    'http://ns.adobe.com/pdf/1.3/': 'pdf',
    'http://ns.adobe.com/xap/1.0/mm/': 'xapmm',
    'http://ns.adobe.com/pdfx/1.3/': 'pdfx',
    'http://prismstandard.org/namespaces/basic/2.0/': 'prism',
    'http://crossref.org/crossmark/1.0/': 'crossmark',
    'http://ns.adobe.com/xap/1.0/rights/': 'rights',
    'http://www.w3.org/XML/1998/namespace': 'xml'
}


class XmpParser(object):

    def __init__(self, xmp):
        self.tree = ET.XML(xmp)
        self.rdftree = self.tree.find(RDF_NS + 'RDF')

    @property
    def read_meta(self):
        """ A dictionary of all the parsed metadata. """
        meta = defaultdict(dict)
        for desc in self.rdftree.findall(RDF_NS + 'Description'):
            #for el in desc.getchildren():
            for el in list(desc):
                ns, tag = self._parse_tag(el)
                value = self._parse_value(el)
                meta[ns][tag] = value
        return dict(meta)

    def _parse_tag(self, el):
        """ Extract the namespace and tag from an element. """
        ns = None
        tag = el.tag
        if tag[0] == "{":
            ns, tag = tag[1:].split('}', 1)
            if ns in NS_MAP:
                ns = NS_MAP[ns]
        return ns, tag

    def _parse_value(self, el):
        """ Extract the metadata value from an element. """
        if el.find(RDF_NS + 'Bag') is not None:
            value = []
            for li in el.findall(RDF_NS + 'Bag/' + RDF_NS + 'li'):
                value.append(li.text)
        elif el.find(RDF_NS + 'Seq') is not None:
            value = []
            for li in el.findall(RDF_NS + 'Seq/' + RDF_NS + 'li'):
                value.append(li.text)
        elif el.find(RDF_NS + 'Alt') is not None:
            value = {}
            for li in el.findall(RDF_NS + 'Alt/' + RDF_NS + 'li'):
                value[li.get(XML_NS + 'lang')] = li.text
        else:
            value = el.text
        return value