low memory rescale of huge image loaded from disk iPhone/iPad

Question

Hello,

I would like to ask if someone has some cue. I load a big image from webserver using ASIHTTP framework directly to the disk. Images about 4096x4096 px.

I need to present this image to user on screen, so I would need to rescale the big image from disk to some considerable resolution lets say 1024x1024 px. The problem for now is that I can rescale it but it needs to load the whole image from disk to memory and scale it there. It obviously is not the best, because sometimes the app gets crash for memory usage.

I have been looking on CATiledLayer examples, this ones works if you have series of tilled images.

Problem is that I have a one big image...

Anybody knows about how possibly could be done? Any help

Thanks.