Sometimes you overlook the easiest solutions. I had implemented a wrapping bitmap in actionscript 2, by some complex copyPixels code, which would cut 1 to 4 pieces from the original image and put them together again, providing you with a bitmap that wraps.
Then I realized that there is a much easier solution, with more functionality as well (not only wrapping but tiling too). But surprised however that it performed much better too. Surprised because I would have thought that 4 copyPixel operations would have been faster than using the drawing API combined with beginBitmapFill.
I’ve wrapped (no pun intended) the idea into two utility classes, the first WrappingBitmap is a simple sprite which takes a bitmapdata as source and creates a tiling wrapping display object that you can scroll.
The second is a WrappingBitmapData class which subclasses BitmapData and overrides the scroll method to wrap.
The demo is the pattern below. Click on the demo to give it focus and scroll using the cursor keys.