It will be huge waste of memory if that big bmp was in memory at one. So I'l make a lot of 2880x2880 and load one file, scroll it at the stage, discard it, load another, scroll it, etc.

What's the best way to connect those two 2880 bmp's to make scrolling fast and smooth?

For copyPixels I need to use a small rectangle from first bmp and small from second and glue those rectangles at showstageRect.

if yellow and green smiley represent 2 big bmp's half of the copyPixels rect will be at yellow and a another half will be at the green smiley.

For scrollRect I need to make overlapping bmp's.

If stageRect is at a corners of 4 big bmps, calculation gets even worse.

And that's where my ideas end
Is there any better way?