UIScrollView animation laggy

Question

Hello,

I'm writing an reader for iPad that shows images (1024x1322 max) in a UIScrollView

each image is loaded in a background thread when it's needed (during scroll) (there is always 3 images loaded at max).

My problem is: when the data is loaded I'm updating the UIImageView, in my background thread like that:

image= [[UIImage alloc] initWithContentsOfFile: file];
[content setImage:image]

It seems to 'lock' the main thread and make the UISCrollView animation not smooth at all.

Thank you in advance for any clue