Drawing route/lines on a custom map image (iphone)

I have a custom map image of an area.. There are about 9 regions and the number of distinct lines needed is only 11 (based on all possible routes).

What is the best way to draw a route on th开发者_如何学运维e map?

The brute force/hacky way is to create static images of every route possible- insane as it amounts to over a million images. Another way is to have layered images with the lines as images on top of the map (is this possible? Would zooming mess it up?)... Any other suggestions to tackle this? I could programmatically draw lines on top of the map but would it be responsive to zooming and such?

Note: The map image is a vectored image (svg) and does not contain GPS coordinates

Thank you!

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You'll probably want to check out coreGraphics, it's perfectly suited for this task. Zooming and all.