Scaling for Multiple Resolutions iOS / Android


I’m developing a small mobile game, targeting both iOS and Android devices.
I’m struggling with the resolution issue, since iPhone devices have some different resolutions and the retina factor; and Android has a lot more different resolutions to deal with.

Is there anyway I could have the images on my game drawn to one single resolution and resized / scaled by the application in runtime?
If I could have an example as a reference, would be really great.

I really appreciate any help I can get.

Best wishes!