Initial implementation of writing XMP metadata to PDF

Lots more work/testing needed

src/calibre/ebooks/metadata/xmp.py

@@ -8,30 +8,40 @@ __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import re, sys
 from itertools import repeat
+from collections import defaultdict
 
 from lxml import etree
+from lxml.builder import ElementMaker
 
+from calibre import replace_entities
 from calibre.ebooks.metadata import check_isbn
 from calibre.ebooks.metadata.book.base import Metadata
-from calibre.utils.date import parse_date
+from calibre.utils.date import parse_date, isoformat, now
 
 _xml_declaration = re.compile(r'<\?xml[^<>]+encoding\s*=\s*[\'"](.*?)[\'"][^<>]*>', re.IGNORECASE)
 
 NS_MAP = {
     'rdf': 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
     'dc': 'http://purl.org/dc/elements/1.1/',
+    'pdf': 'http://ns.adobe.com/pdf/1.3/',
+    'pdfx': 'http://ns.adobe.com/pdfx/1.3/',
     'xmp': 'http://ns.adobe.com/xap/1.0/',
     'xmpidq': 'http://ns.adobe.com/xmp/Identifier/qual/1.0/',
-    'pdf': 'http://ns.adobe.com/pdf/1.3/',
+    'xmpMM': 'http://ns.adobe.com/xap/1.0/mm/',
-    'xmpmm': 'http://ns.adobe.com/xap/1.0/mm/',
+    'xmpRights': 'http://ns.adobe.com/xap/1.0/rights/',
-    'pdfx': 'http://ns.adobe.com/pdfx/1.3/',
+    'xmpBJ': 'http://ns.adobe.com/xap/1.0/bj/',
+    'xmpTPg': 'http://ns.adobe.com/xap/1.0/t/pg/',
+    'xmpDM': 'http://ns.adobe.com/xmp/1.0/DynamicMedia/',
     'prism': 'http://prismstandard.org/namespaces/basic/2.0/',
     'crossmark': 'http://crossref.org/crossmark/1.0/',
-    'rights': 'http://ns.adobe.com/xap/1.0/rights/',
+    'xml': 'http://www.w3.org/XML/1998/namespace',
-    'xml': 'http://www.w3.org/XML/1998/namespace'
+    'x': 'adobe:ns:meta/',
+    'calibre': 'http://calibre-ebook.com/xmp-namespace',
 }
+KNOWN_ID_SCHEMES = {'isbn', 'url', 'doi'}
 
-def NS(prefix, name):
+def expand(name):
+    prefix, name = name.partition(':')[::2]
     return '{%s}%s' % (NS_MAP[prefix], name)
 
 xpath_cache = {}
@@ -68,8 +78,8 @@ def serialize_xmp_packet(root, encoding='utf-8'):
 def read_simple_property(elem):
     # A simple property
     if elem.text:
-        return elem.text
+        return replace_entities(elem.text)
-    return elem.get(NS('rdf', 'resource'), '')
+    return replace_entities(elem.get(expand('rdf:resource'), ''))
 
 def read_lang_alt(parent):
     # A text value with possibel alternate values in different languages
@@ -111,33 +121,41 @@ def first_alt(expr, root):
             return q
 
 def first_simple(expr, root):
-    # The value for the first occurrence of an element matching exp (assumes
+    # The value for the first occurrence of an element matching expr (assumes
     # simple property)
     for item in XPath(expr)(root):
         q = read_simple_property(item)
         if q:
             return q
 
-def read_xmp_identifer(parent):
+def first_sequence(expr, root):
-    ''' For example:
+    # The first item in a sequence
-    <xmp:Identifier rdf:parseType="Resource"><xmpidq:Scheme>URL</xmp:idq><rdf:value>http://foo.com</rdf:value></xmp:Identifier>
+    for item in XPath(expr)(root):
-    or the longer form:
+        for ans in read_sequence(item):
-    <xmp:Identifier><rdf:Description><xmpidq:Scheme>URL</xmp:idq><rdf:value>http://foo.com</rdf:value></rdf:Description></xmp:Identifier>
+            return ans
-    '''
-    is_resource = parent.attrib.get(NS('rdf', 'parseType'), None) == 'Resource'
-    is_resource = is_resource or (len(parent) == 1 and parent[0].tag == NS('rdf', 'Description'))
-    if not is_resource:
-        return None, None
-    value = XPath('descendant::rdf:value')(parent)
-    if not value:
-        return None, None
-    value = value.text or ''
-    scheme = XPath('descendant::xmpidq:Scheme')(parent)
-    if not scheme:
-        return None, value
-    return scheme.text or '', value
 
-def read_xmp_packet(raw_bytes):
+def read_xmp_identifers(parent):
+    ''' For example:
+    <rdf:li rdf:parseType="Resource"><xmpidq:Scheme>URL</xmp:idq><rdf:value>http://foo.com</rdf:value></rdf:li>
+    or the longer form:
+    <rdf:li><rdf:Description><xmpidq:Scheme>URL</xmp:idq><rdf:value>http://foo.com</rdf:value></rdf:Description></rdf:li>
+    '''
+    for li in XPath('./rdf:Bag/rdf:li')(parent):
+        is_resource = li.attrib.get(expand('rdf:parseType'), None) == 'Resource'
+        is_resource = is_resource or (len(li) == 1 and li[0].tag == expand('rdf:Description'))
+        if not is_resource:
+            yield None, li.text or ''
+        value = XPath('descendant::rdf:value')(li)
+        if not value:
+            continue
+        value = value[0].text or ''
+        scheme = XPath('descendant::xmpidq:Scheme')(li)
+        if not scheme:
+            yield None, value
+        else:
+            yield scheme[0].text or '', value
+
+def metadata_from_xmp_packet(raw_bytes):
     root = parse_xmp_packet(raw_bytes)
     mi = Metadata(_('Unknown'))
     title = first_alt('//dc:title', root)
@@ -156,7 +174,7 @@ def read_xmp_packet(raw_bytes):
     if publishers:
         mi.publisher = publishers[0]
     try:
-        pubdate = parse_date(first_simple('//dc:date', root) or first_simple('//xmp:CreateDate', root), assume_utc=False)
+        pubdate = parse_date(first_sequence('//dc:date', root) or first_simple('//xmp:CreateDate', root), assume_utc=False)
     except:
         pass
     else:
@@ -166,12 +184,12 @@ def read_xmp_packet(raw_bytes):
 
     identifiers = {}
     for xmpid in XPath('//xmp:Identifier')(root):
-        scheme, value = read_xmp_identifer(xmpid)
+        for scheme, value in read_xmp_identifers(xmpid):
             if scheme and value:
                 identifiers[scheme.lower()] = value
 
     for namespace in ('prism', 'pdfx'):
-        for scheme in ('doi', 'url', 'isbn', 'ISBN'):
+        for scheme in KNOWN_ID_SCHEMES:
             if scheme not in identifiers:
                 val = first_simple('//%s:%s' % (namespace, scheme), root)
                 scheme = scheme.lower()
@@ -187,7 +205,7 @@ def read_xmp_packet(raw_bytes):
 def consolidate_metadata(info_mi, xmp_packet):
     ' When both the PDF Info dict and XMP metadata are present, prefer the xmp metadata '
     try:
-        xmp_mi = read_xmp_packet(xmp_packet)
+        xmp_mi = metadata_from_xmp_packet(xmp_packet)
     except:
         import traceback
         traceback.print_exc()
@@ -195,9 +213,187 @@ def consolidate_metadata(info_mi, xmp_packet):
         info_mi.smart_update(xmp_mi, replace_metadata=True)
     return info_mi
 
+def nsmap(*args):
+    return {x:NS_MAP[x] for x in args}
+
+def create_simple_property(parent, tag, value):
+    e = parent.makeelement(expand(tag))
+    parent.append(e)
+    e.text = value
+
+def create_alt_property(parent, tag, value):
+    e = parent.makeelement(expand(tag))
+    parent.append(e)
+    alt = e.makeelement(expand('rdf:Alt'))
+    e.append(alt)
+    li = alt.makeelement(expand('rdf:li'))
+    alt.append(li)
+    li.set(expand('xml:lang'), 'x-default')
+    li.text = value
+
+def create_sequence_property(parent, tag, val, ordered=True):
+    e = parent.makeelement(expand(tag))
+    parent.append(e)
+    seq = e.makeelement(expand('rdf:' + ('Seq' if ordered else 'Bag')))
+    e.append(seq)
+    for x in val:
+        li = seq.makeelement(expand('rdf:li'))
+        li.text = x
+        seq.append(li)
+
+def create_identifiers(xmp, identifiers):
+    xmpid = xmp.makeelement(expand('xmp:Identifier'))
+    xmp.append(xmpid)
+    bag = xmpid.makeelement(expand('rdf:Bag'))
+    xmpid.append(bag)
+    for scheme, value in identifiers.iteritems():
+        li = bag.makeelement(expand('rdf:li'))
+        li.set(expand('rdf:parseType'), 'Resource')
+        bag.append(li)
+        s = li.makeelement(expand('xmpidq:Scheme'))
+        s.text = scheme
+        li.append(s)
+        val = li.makeelement(expand('rdf:value'))
+        li.append(val)
+        val.text = value
+
+def metadata_to_xmp_packet(mi):
+    A = ElementMaker(namespace=NS_MAP['x'], nsmap=nsmap('x'))
+    R = ElementMaker(namespace=NS_MAP['rdf'], nsmap=nsmap('rdf'))
+    root = A.xmpmeta(R.RDF)
+    rdf = root[0]
+    dc = rdf.makeelement(expand('rdf:Description'), nsmap=nsmap('dc'))
+    dc.set(expand('rdf:about'), '')
+    rdf.append(dc)
+    for prop, tag in {'title':'dc:title', 'comments':'dc:description'}.iteritems():
+        val = mi.get(prop) or ''
+        create_alt_property(dc, tag, val)
+    for prop, (tag, ordered) in {
+        'authors':('dc:creator', True), 'tags':('dc:subject', False), 'publisher':('dc:publisher', False),
+    }.iteritems():
+        val = mi.get(prop) or ()
+        if isinstance(val, basestring):
+            val = [val]
+        create_sequence_property(dc, tag, val, ordered)
+    if not mi.is_null('pubdate'):
+        create_sequence_property(dc, 'dc:date', [isoformat(mi.pubdate, as_utc=False)])  # Adobe spec recommends local time
+
+    xmp = rdf.makeelement(expand('rdf:Description'), nsmap=nsmap('xmp', 'xmpidq'))
+    xmp.set(expand('rdf:about'), '')
+    rdf.append(xmp)
+    extra_ids = {}
+    for x in ('prism', 'pdfx'):
+        p = extra_ids[x] = rdf.makeelement(expand('rdf:Description'), nsmap=nsmap(x))
+        p.set(expand('rdf:about'), '')
+        rdf.append(p)
+
+    identifiers = mi.get_identifiers()
+    if identifiers:
+        create_identifiers(xmp, identifiers)
+        for scheme, val in identifiers.iteritems():
+            if scheme in {'isbn', 'doi'}:
+                for prefix, parent in extra_ids.iteritems():
+                    ie = parent.makeelement(expand('%s:%s'%(prefix, scheme)))
+                    ie.text = val
+                    parent.append(ie)
+
+    d = xmp.makeelement(expand('xmp:MetadataDate'))
+    d.text = isoformat(now(), as_utc=False)
+    xmp.append(d)
+
+    return serialize_xmp_packet(root)
+
+def find_used_namespaces(elem):
+    getns = lambda x: (x.partition('}')[0][1:] if '}' in x else None)
+    ans = {getns(x) for x in list(elem.attrib) + [elem.tag]}
+    for child in elem.iterchildren(etree.Element):
+        ans |= find_used_namespaces(child)
+    return ans
+
+def find_preferred_prefix(namespace, elems):
+    for elem in elems:
+        ans = {v:k for k, v in elem.nsmap.iteritems()}.get(namespace, None)
+        if ans is not None:
+            return ans
+        return find_preferred_prefix(namespace, elem.iterchildren(etree.Element))
+
+def find_nsmap(elems):
+    used_namespaces = set()
+    for elem in elems:
+        used_namespaces |= find_used_namespaces(elem)
+    ans = {}
+    used_namespaces -= {NS_MAP['xml'], NS_MAP['x'], None, NS_MAP['rdf']}
+    rmap = {v:k for k, v in NS_MAP.iteritems()}
+    i = 0
+    for ns in used_namespaces:
+        if ns in rmap:
+            ans[rmap[ns]] = ns
+        else:
+            pp = find_preferred_prefix(ns, elems)
+            if pp and pp not in ans:
+                ans[pp] = ns
+            else:
+                i += 1
+                ans['ns%d' % i] = ns
+    return ans
+
+def clone_into(parent, elem):
+    ' Clone the element, assuming that all namespace declarations are present in parent '
+    clone = parent.makeelement(elem.tag)
+    parent.append(clone)
+    if elem.text and not elem.text.isspace():
+        clone.text = elem.text
+    if elem.tail and not elem.tail.isspace():
+        clone.tail = elem.tail
+    clone.attrib.update(elem.attrib)
+    for child in elem.iterchildren(etree.Element):
+        clone_into(clone, child)
+
+def merge_xmp_packet(old, new):
+    ''' Merge metadata present in the old packet that is not present in the new
+    one into the new one. Assumes the new packet was generated by
+    metadata_to_xmp_packet() '''
+    old, new = parse_xmp_packet(old), parse_xmp_packet(new)
+    # As per the adobe spec all metadata items have to be present inside top-level rdf:Description containers
+    item_xpath = XPath('//rdf:RDF/rdf:Description/*')
+
+    # First remove all data fields that are defined in the new packet from the
+    # old packet
+    defined_tags = {expand(prefix + ':' + scheme) for prefix in ('prism', 'pdfx') for scheme in KNOWN_ID_SCHEMES}
+    defined_tags |= {x.tag for x in item_xpath(new)}
+    for elem in item_xpath(old):
+        if elem.tag in defined_tags:
+            elem.getparent().remove(elem)
+
+    # Group all items into groups based on their namespaces
+    groups = defaultdict(list)
+    for item in item_xpath(new):
+        ns = item.nsmap[item.prefix]
+        groups[ns].append(item)
+
+    for item in item_xpath(old):
+        ns = item.nsmap[item.prefix]
+        groups[ns].append(item)
+
+    A = ElementMaker(namespace=NS_MAP['x'], nsmap=nsmap('x'))
+    R = ElementMaker(namespace=NS_MAP['rdf'], nsmap=nsmap('rdf'))
+    root = A.xmpmeta(R.RDF)
+    rdf = root[0]
+
+    for namespace in sorted(groups, key=lambda x:{NS_MAP['dc']:'a', NS_MAP['xmp']:'b', NS_MAP['calibre']:'c'}.get(x, 'z'+x)):
+        items = groups[namespace]
+        desc = rdf.makeelement(expand('rdf:Description'), nsmap=find_nsmap(items))
+        desc.set(expand('rdf:about'), '')
+        rdf.append(desc)
+        for item in items:
+            clone_into(desc, item)
+
+    return serialize_xmp_packet(root)
 
 if __name__ == '__main__':
     from calibre.utils.podofo import get_xmp_metadata
     xmp_packet = get_xmp_metadata(sys.argv[-1])
-    print (read_xmp_packet(xmp_packet))
+    mi = metadata_from_xmp_packet(xmp_packet)
+    np = metadata_to_xmp_packet(mi)
+    print (merge_xmp_packet(xmp_packet, np))
 

src/calibre/utils/podofo/__init__.py

@@ -30,9 +30,12 @@ def set_metadata(stream, mi):
     with TemporaryDirectory(u'_podofo_set_metadata') as tdir:
         with open(os.path.join(tdir, u'input.pdf'), 'wb') as f:
             shutil.copyfileobj(stream, f)
+        from calibre.ebooks.metadata.xmp import metadata_to_xmp_packet
+        xmp_packet = metadata_to_xmp_packet(mi)
+
         try:
             touched = fork_job('calibre.utils.podofo', 'set_metadata_', (tdir,
-                mi.title, mi.authors, mi.book_producer, mi.tags))
+                mi.title, mi.authors, mi.book_producer, mi.tags, xmp_packet))
         except WorkerError as e:
             raise Exception('Failed to set PDF metadata: %s'%e.orig_tb)
         if touched:
@@ -46,7 +49,7 @@ def set_metadata(stream, mi):
                     stream.flush()
     stream.seek(0)
 
-def set_metadata_(tdir, title, authors, bkp, tags):
+def set_metadata_(tdir, title, authors, bkp, tags, xmp_packet):
     podofo = get_podofo()
     os.chdir(tdir)
     p = podofo.PDFDoc()
@@ -75,6 +78,16 @@ def set_metadata_(tdir, title, authors, bkp, tags):
     except:
         pass
 
+    try:
+        current_xmp_packet = p.get_xmp_metadata()
+        if current_xmp_packet:
+            from calibre.ebooks.metadata.xmp import merge_xmp_packet
+            xmp_packet = merge_xmp_packet(current_xmp_packet, xmp_packet)
+        p.set_xmp_metadata(xmp_packet)
+        touched = True
+    except:
+        pass
+
     if touched:
         p.save(u'output.pdf')