saving image files with *Agg backends

Hi Everyone, I'm having trouble saving plot images with

    > the *Agg backends. I've tried TkAgg, GTKAgg, WXAgg, and
    > get the following error message (here for WXAgg):

    > Do not know how to handle extension *.jpg 14:48:54 Debug
    > e:\Projects\wx2.4\src\msw\app.cpp(439):
    > 'UnregisterClass(canvas)' failed with error 0x00000584
    > (class still has open windows)

    > WX and GTK backends work. I'm using the precompiled 0.60.2
    > version of Matplotlib (congratulations on the new
    > release), python 2.3.4, windows XP. I'm calling my program
    > from a DOS prompt to get the error messages, working in
    > non-interactive mode and trying to save the image using
    > the save-button widget.

The agg backend can only save png, ps, eps, and svg. jpeg is
available from backend_wx and backend_gtk. Personally, I've never
encountered a figure for which jpeg was a better output format than
png, which is why I haven't worked to provide a jpeg output to agg,
but it would be a good thing to add, at some point.