Added a section on custom XMP namespaces to the tutorial.

1 files changed, 13 insertions, 0 deletions

diff --git a/doc/tutorial.rst b/doc/tutorial.rst
index 9f5a418..709b686 100644
--- a/doc/tutorial.rst
+++ b/doc/tutorial.rst
@@ -240,6 +240,19 @@ If the tag was not present, one is created and its value is set::
 
   >>> metadata[key] = value
 
+If you need to write custom metadata, you can register a custom XMP namespace::
+
+  >>> pyexiv2.xmp.register_namespace('http://example.org/foo/', 'foo')
+  >>> metadata['Xmp.foo.bar'] = 'baz'
+
+Note that a limitation of the current implementation is that only simple text
+values can be written to tags in a custom namespace.
+
+A custom namespace can be unregistered. This has the effect of invalidating all
+tags in this namespace for images that have not been written back yet::
+
+  >>> pyexiv2.xmp.unregister_namespace('http://example.org/foo/')
+
 Accessing embedded previews
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