Question

I am trying to zoom into a UIImage so I can see as much of the photo as possible without showing white space. Thus in portrait I want to zoom so that the shorter of the two sides of the image fits fully in the screen. All of the following code is in viewDidLoad.

I have the UIImageView and UIScrollView set up as follows:

self.scrollView.delegate = self;
self.scrollView.contentSize = self.imageView.image.size;
self.imageView.frame = CGRectMake(0, 0, IMAGE_WIDTH, IMAGE_HEIGHT);

At this point zooming and scrolling within the UIScrollView works perfectly.

Then I implement an if-else so that when the picture is taller than it is wide I call:

[self.scrollview zoomToRect:CGRectMake(0, 0, IMAGE_WIDTH, 1)];

This works perfectly. The width of the image fills the width of the screen and I can only scroll up and down.

But when I call the exact same function for the height:

[self.scrollview zoomToRect:CGRectMake(0, 0, 1, IMAGE_HEIGHT)];

Nothing! No zoom at all as if the function was never called. But I set a breakpoint and stepped through the code in the debugger and everything was called perfectly, even the CGRectMake function itself. What’s going on?

Answer 1

As per the comments above, make sure you select a rect with both a width and a height for the given aspect ratio you want to zoom to.

[self.scrollview zoomToRect:CGRectMake(0, 0, IMAGE_WIDTH * WIDTH_OF_VIEW / HEIGHT_OF_VIEW, IMAGE_HEIGHT)];