How do I pan the image inside a UIImageView?

Question

I have a UIImageView that is displaying an image that is wider and taller than the UIImageView is. I would like to pan the image within the view us

Answer 1

Brad Larson pointed me down the right road with his suggestion to put the UIImageView inside a UIScrollView.

In the end I put the UIImageView inside of a UIScrollView, and set the scrollView's contentSize and the imageView's bounds to be the same size as the image in the UIImage:

UIImage* image = imageView.image;
imageView.bounds = CGRectMake(0, 0, image.size.width, image.size.height);
scrollView.contentSize = image.size;

Then, I can animate the scrollView's contentOffset to achieve a nice panning effect:

[UIView beginAnimations:@"pan" context:nil];
[UIView setAnimationDuration:animationDuration];
scrollView.contentOffset = newRect.origin;
[UIView commitAnimations];

In my particular case, I'm panning to a random space in the image. In order to find a proper rect to pan to and a proper duration to get a nice constant speed, I use the following:

UIImage* image = imageView.image;

float xNewOrigin = [TCBRandom randomIntLessThan:image.size.width - scrollView.bounds.size.width];
float yNewOrigin = [TCBRandom randomIntLessThan:image.size.height - scrollView.bounds.size.height];

CGRect oldRect = scrollView.bounds;
CGRect newRect = CGRectMake(
    xNewOrigin,
    yNewOrigin, 
    scrollView.bounds.size.width,
    scrollView.bounds.size.height);

float xDistance = fabs(xNewOrigin - oldRect.origin.x);
float yDistance = fabs(yNewOrigin - oldRect.origin.y);
float hDistance = sqrtf(powf(xDistance, 2) + powf(yDistance, 2));
float hDistanceInPixels = hDistance;

float animationDuration = hDistanceInPixels / speedInPixelsPerSecond;

I'm using a speedInPixelsPerSecond of 10.0f, but other applications might want to use a different value.