ScriptPictureEffects doesn't handle resizing canvases

```
Need to change - currently ScriptPictureEffects takes a Graphics pointer in
UseImages which is the
backdrop of a canvas. If you had a canvas that resized its backdrop, that would
be a new picture
and UseImages would have to be called again.

If you continuall call UseImages every time the script is run, it is not a
problem but is a bit
confusing in this sample if people edit the sample to make the canvas resize in
response to window
resizing.
```

Original issue reported on code.google.com by `dentaroo@gmail.com` on 25 Apr 2009 at 5:14