OpenRaster does not yet make any suggestions on how to store metadata. My preference is for OpenRaster to continue to borrow from OpenDocument and use the same format meta.xml file, but that can be complicated. Rather than taking the time to write a whole lot of code and waiting do metadata the best way, I found another way that is good enough, and expedient. I think ordinary users will find it useful -- which is the most important thing -- to be able to round-trip metadata in the OpenRaster format, so despite my reservations about creating code that might discourage developers (myself included) from doing things a better way in future I am choosing the easy option. (In my previous post I mentioned my concern about maintainability, this is what I was alluding to.)
A lot of work has been done over the years to make the The GNU Image Manupilation Program (GIMP) work with existing standards. One of those standards is XMP, the eXtensible Metadata Platform originally created by Adobe Systems, which used the existing Dublin Core metadata standard to create XML packets that can be inserted inside (or alongside) an image file. The existing code creates an XMP packet, let's call it
packet.xmpand include it in the OpenRaster file. There's a little more code to the load the information back in and users should be able to go to menu
File, Propertiesand in Properties dialog go to the tab labelled Advanced to view (or set) metadata.
This approach may not be particularly useful to users who want to get their information out into other applications such as MyPaint or Krita (or Drawpile or Lazpaint) but it at least allows them not to lose metadata information when they use OpenRaster. (In the long run other programs will probably want to implement code to read XMP anyway, so I think this is a reasonable compromise, even though I want OpenRaster to stay close to OpenDocument and benefit from being part of that very large community.)
You can get the updated plugin immediately from the OpenRaster plugin gitorious project page.
If you are a developer and want to modify or reuse the code, it is published under the ISC License.