For those people who are a little confused try this:

1. Go into Photoshop and make a new image, say 5000×5000 in size. Clear it so it’s totally transparent.
2. Save the image as a PNG. You cannot use the “Save for web…” option as it can’t handle images this large.
3. In Flash go to File -> Import to library. Choose the file you’ve just made in Photoshop.
4. Find the file you just imported in your library. Right click it and go to “Linkage…”
5. Click on the “Export for Actionscript” and then give it a name ie “E_LargeBitmap”
6. In your AS3 code you can put in a line of code like the following:

var largeBitmap:BitmapData = new E_LargeBitmap(5000, 5000);

You’ll now have a blank bitmap data (at least completely transparent one) that is super large (25 Megapixel image anyone?).

Have fun!

Thanks.