Is JNT really a proprietary binary format?
Ok , couple of things first. Ink is ink and i would rather it stayed ink. That probably means i would rather have the actual serialized object . Thats where ISF shows up.

Ink Serialized Format (ISF) , the most compact persistent representation of ink is extensible with custom attributes (identified by a GUID) and allows you to store any kind of data or metadata as an attribute in an ISF stream.

Alright , and .....ISF is a format specific to Windows XP Tablet PC Edition, and the only way you can get at ISF is to use the Ink object's Load and Save methods.....

everything else starts after ISF.
For best performance and total control of ink ISF is the way to go with whatever enhancements you need to work with ink

For heterogeneous content, use fortified GIFs to encode ink into HTML documents. Browsers and html's hyper linking are your friend in that situation

For Images you could move bitmap and metafile that are got from inks conversion to GIF

And we can alsoe encode ink in the RTF as OLE objects. This is very useful for pasting into an OLE container, such as Microsoft Word.

and of course the most useful format is XML .

the are 4 supported PersistenceFormat, though it essentially is 2 formats , you can go anywhere from this. Actually go any where and come back ...

enum PersistenceFormat {
InkSerializedFormat = 0,
Base64InkSerializedFormat = 1,
Gif = 2,
Base64Gif = 3
};