JNI bridge to batik

[Xavier Wielemans <wi...@alterface.net>]

Hi all,

Involved in a big C++ software project (virtual reality engine) I tried to 
integrate batik into our system for real-time svg rendering (as it is the 
only working open-source svg renderer available - to my knowledge anyway - 
if you know better, PLEASE inform me, thx !).

Therefore I used JNI to bridge batik to our system.  I have create an 
"SVGLayer" Java class (right, the name is not very pertinent... :)  It was 
just a prototype...) which uses batik to load an svg document (in its 
constructor) and render it inside a "scene" area, based on a given scale, 
rotation, position in the scene and global scene dimensions.  To do that, 
it will compute the exact shape of the rendering result, in the scene coord 
space (by scaling/rotating/translating the svg document's rectangular 
bounding box, then clipping the resulting bounding box wrt. the scene 
boundaries) and apply to that shape the inverse transform, which gives the 
area to be rendered, in the svg document coord space (thanks to this, only 
the effectively visible part of the svg doc will be rendered).  Finally the 
rendering buffer can be retrieved (dimensions and data) as an int array 
(32-bit RGBA pixels) so you can use it in any other software to blend it in 
your own creations, for instance.

Unfortunately for us, the performance is far from enough for our 
needs.  But I hope it can at least help someone else ! ;)

Here is the SVGLayer's class javadoc + the source file.  If you are 
interested, I can also send a C++ sample prog showing how to use it through 
JNI (it works fine but it needs some extra reformatting work, so I'll do it 
only if there is interest for it).  The good news is that JNI data transfer 
doesn't diminish overall performance that much, so it is pretty usable and 
fast if you don't need a high real-time framerate.  And of course you get 
the excellent batik rendering quality (antialiasing etc.) !

BTW, it is not designed to support dynamic svg docs (scripting, 
animations,...) so I really don't know what happens if you run it on one of 
those...

Hope this helps, any comments, suggestions, critics, requests for 
additional details, build scripts... welcome !

See ya,

Willy.

Xavier Wielemans - alterface
http://www.alterface.com