1. I did not know there were any native compilers left but Jet and
gcj.  What is this called?  Is it just a wrapper or a true AOT
optimising compiler? Do you have to buy something to use this? I am
asking this not to solve your problem but for the Java glossary.

2. Is this correct?  Jimi is a pure Java package  com.sun.jimi for
reading and saving various formats of image files, such as GIF and
JPG. It was originally a third party package, but Sun now owns it. In
Java 1.2+ it was replaced by Advanced Imaging classes such as
com.sun.image.codec.jpeg.JPEGImageEncoder interface. In Java 1.4+ you
have ImageIO.  Jimi is  no longer distributed as part of the JDK.

So it looks as if you you have to do something special to get the Jimi
classes on the classpath.

I would assume your native compiler would need access to the class
files so it could include them in the exe file it produces.  

Your big problem is there is no error message, just a blank image,
correct?, as if you had executed null methods, or they were improperly
compiled.

Your AOT may or may not be able to handle dynamically loaded classes.
You may have to manually include them when you build your exe.  Even
if it can, perhaps it is having trouble finding a class, and the error
message is getting lost because you swallowed an exception.

If I were in your shoes here is how I would proceed:

0. check the buglist for the compiler to see if anyone else has
reported similar problem.

1. decide if this is important enough to throw more time into.

2. search the code near the problem for any place it might quietly
swallow an exception and do a stack trace instead.

3. check the compile time and run time classpaths to be sure all
plausible classes are available.

4. see if there is some feature to manually include dynamically loaded
classes, and manually include more classes than you think necessary.
If it works, prune back.

5. try compiling with the evaluation version of Jet, another AOT
compiler,  to see if it has the same problem. If it does, it may give
different messages that may give a clue.  See
http://mindprod.com/jgloss/jet.html