The problem is you're mixing up logical and pixel sizes. On non retina devices these two are the same, but on retina devices (like in your case) the pixel size is actually double the logical size.
Usually, when designing your GUI, you can always just think in logical sizes and coordinates, and iOS (or OS X) will make sure, that everything is doubled on retina screens. However, in some cases, especially when creating images yourself, you have to explicitly specify what size you mean.
UIImage
's size
method returns the logical size. That is the resolution on non-retina screens for instance. This is why CGImageCreateWithImageInRect
will only create an new image, from the upper left half of the image.
Multiply your logical size with the scale of the image (1 on non-retina devices, 2 on retina devices):
CGFloat originalWidth = pic.size.width * pic.scale;
CGFloat originalHeight = pic.size.height * pic.scale;
This will make sure, that the new image is created from the full height (or width) of the original image. Now, one remaining problem is, that when you create a new UIImage
using
UIImage *squareImage = [UIImage imageWithCGImage:imageRef];
iOS will think, this is a regular, non-retina image and it will display it twice as large as you would expect. To fix this, you have to specify the scale when you create the UIImage
:
UIImage *squareImage = [UIImage imageWithCGImage:imageRef
scale:pic.scale
orientation:pic.imageOrientation];