I'm working on an app that shows a thumbnail of a photo taken by the user. In order to show a seemless transition from the full-screen image shown in the UIImagePickerController to the thumbnail, I set the frame on my copy of the image to [[UIScreen mainScreen] bounds] and then change the frame to match the frame of an invisible button. (The button allows users to re-take their photo by tapping the thumbnail image.)

The trouble is that the starting x-origin of my UIImageView (imageView) is mysteriously starting nearly offscreen to the left:

As you can see from the alert, the imageView purports to be located at (0,0), yet it's displaying at something like (-255,0). Here's the code:

CGRect frame = [[UIScreen mainScreen] bounds];
imageView.frame = frame;

[[[[UIAlertView alloc] initWithTitle:@"Yo!" message:[NSString stringWithFormat:@"starting frame:%@",NSStringFromCGRect(imageView.frame)] delegate:nil cancelButtonTitle:@"K." otherButtonTitles:nil] autorelease] show];

// Slide the enlarged image seamlessly "onto" the photo button
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:1000];
[UIView setAnimationDelay:.5];

imageView.frame = pictureButton.frame;

[UIView commitAnimations];

As if to taunt me, the image actually does go full screen if I comment out the animation code:

CGRect frame = [[UIScreen mainScreen] bounds];
imageView.frame = frame;

[[[[UIAlertView alloc] initWithTitle:@"Yo!" message:[NSString stringWithFormat:@"starting frame:%@",NSStringFromCGRect(imageView.frame)] delegate:nil cancelButtonTitle:@"K." otherButtonTitles:nil] autorelease] show];

// Slide the enlarged image seamlessly "onto" the photo button
//    [UIView beginAnimations:nil context:nil];
//    [UIView setAnimationDuration:1000];
//    [UIView setAnimationDelay:.5];
//    
//    imageView.frame = pictureButton.frame;
//    
//    [UIView commitAnimations];

(Note: animationDuration will of course be set to something more like .5 in production, not 1000 seconds.)

Update — Other weirdness worth mentioning in case it's relevant:

• It turns out the offset changes depending on the orientation of the camera when the photo was taken. If I take the picture with the phone upside-down, for instance, then the image gets offset vertically as well as horizontally.
• The picker seems to be filling the image's imageOrientation incorrectly: I have to hold the phone sideways, Home button on the left, to get an image with UIImageOrientationUp.
• At one point I experimented with setting imageView.clipsToBounds = YES;, which revealed that my image view's frame is in fact correct. Rather, it's the UIImage's placement within the UIImageView that gets offset.
• Fwiw, the image view's contentMode is the default, UIViewContentModeScaleToFill.