Question

I have an imageview that has a pinchgesturerecognizer attached to it. In the pinchgesturerecognizer delegate method, I need to calculate the frame value of the transformation before it occurs in order to see if the scaling has pushed the imageview out of the bounds of the window. I know I need to use CGRectApplyAffineTransform to calculate the frame value each time, but since the imageview frame value will be invalid after the first transformation gets performed, do I need to now store the update frame value in an instance variable and keep updating it everytime a transform occurs, or is there someway I can obtain this value from the imageview itself?

Answer 1

So you want to check if a UIImageView is inside its window?

I think you can ignore the view frame and instead start your calculations
from the view bounds. This will include the transformation you have applied to the view.

Apple has a section named The Relationship of the Frame, Bounds, and Center Properties in the View Programming Guide for iOS.

CGRect imageViewBounds = imageView.bounds;
CGRect imageViewBoundsInWindow = [imageView convertRect:imageViewBounds
                                                 toView:nil];
CGRect windowBounds = imageView.window.bounds;
if ( CGRectIntersectsRect( windowBounds, imageViewBoundsInWindow ) ) {
     // imageView is visible in its window
}