Creating an image magnification inside an instance of UIScrollView - iphone

Question

I have an instance of UIScrollView with images inside it.
It is possible to scroll the scroll view horizontally, and view more images.
I want to magnify the images, according the their distance from the middle of the scroll view, so it should look like this.
I thought about the simplest way to do that, using the following code:
- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
//Change the frames of all the visible images here.
}
This way does not work smoothly on some of the preceding devices, such as iPod 2G.
Is there a better way to perform the image magnification than the one I described?
If so, please let me know.
Thanks!
EDIT:
This is the implementation of the body of the method above:
-(void) magnifyImages {
//This method magnifies all the images.
for (NSString *name in [imagesDict allKeys]) {
UIImageView *imageView = [imagesDict objectForKey:name];
[self magnifyImageView:imageView];
}
}
static float kMaxMagnification = 1.5;
-(void) magnifyImageView:(UIImageView *)imageView {
CGRect frame = imageView.frame;
float imageMiddleLine = frame.origin.x+frame.size.width/2-scrollView.contentOffset.x;
//Check if the image's middle line is visible = whether it is needed to magnify the image.
if (imageMiddleLine +frame.size.width/2>0
&& imageMiddleLine-frame.size.width/2<scrollView.frame.size.width) {
float magnification = fabs(160-imageMiddleLine);
//Mathematical formula that calculates the magnification.
magnification = (kMaxMagnification-1)*(kDeviceWidth/2-magnification)/160+1;
//'normalImageSize' is a property of the image that returns the image's normal size (when not magnified).
CGSize imgSize = imageView.normalImageSize;
frame=CGRectMake(frame.origin.x-(imgSize.width*magnification-frame.size.width)/2,
frame.origin.y-(imgSize.height*magnification-frame.size.height)/2,
imgSize.width*magnification, imgSize.height*magnification);
imageView.frame=frame;
}
}