Merge branch 'issue21' into devel

docs/source/how_do_i.rst

@@ -27,3 +27,35 @@ display just raw codestream as well. This will display metadata present in the
 codestream's main header only. ::
 
     >>> print(j.get_codestream())
+
+Work with XMP UUIDs?
+====================
+The example JP2 file shipped with glymur has an XMP UUID::
+
+    >>> import pkg_resources
+    >>> from glymur import Jp2k
+    >>> file = pkg_resources.resource_filename(glymur.__name__, "data/nemo.jp2")
+    >>> j = Jp2k(file)
+    >>> print(j.box[4])
+    UUID Box (uuid) @ (715, 2412)
+        UUID:  be7acfcb-97a9-42e8-9c71-999491e3afac (XMP)
+        UUID Data:  
+        <ns0:xmpmeta xmlns:ns0="adobe:ns:meta/" xmlns:ns2="http://ns.adobe.com/xap/1.0/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" ns0:xmptk="XMP Core 4.4.0-Exiv2">
+          <rdf:RDF>
+            <rdf:Description ns2:CreatorTool="glymur" rdf:about="" />
+          </rdf:RDF>
+        </ns0:xmpmeta>
+
+Since the UUID data in this case is returned as an ElementTree Element, one can
+use ElementTree to access the data.  For example, to extract the 
+**CreatorTool** attribute value, the following would work::
+
+    >>> xmp = j.box[4].data
+    >>> ns0 = '{http://www.w3.org/1999/02/22-rdf-syntax-ns#}'
+    >>> ns1 = '{http://ns.adobe.com/xap/1.0/}'
+    >>> name = '{0}RDF/{0}Description'.format(ns0)
+    >>> elt = xmp.find(name)
+    >>> elt
+    <Element '{http://www.w3.org/1999/02/22-rdf-syntax-ns#}Description' at 0xb4baa93c>
+    >>> elt.attrib['{0}CreatorTool'.format(ns1)]
+    'glymur'