How to align a mask in an image

Question

I am writing in Swift trying to mask an image using UIImage and CALayer. The problem is that the mask is scaled and shifted when applied to the image. I created my UIImageViewer using Interface Builder and I installed it in Aspect Fit. I would like to mask images of arbitrary size. I am creating a mask image of the same size as the image. This is a requirement because later I want to programmatically add elements to the mask in the mask, and it should cover the masked image. Here is my code:

class ViewController: UIViewController {

@IBOutlet weak var imageView: UIImageView!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    var img = UIImage(named: "flowers.png")

    var maskImageSize = CGSizeMake(img!.size.width, img!.size.height)

    UIGraphicsBeginImageContextWithOptions(maskImageSize, false, 0.0)

    var color = UIColor(white: 1.0, alpha: 0.0)
    color.setFill()
    var rect = CGRectMake(0, 0, img!.size.width, img!.size.height)
    UIRectFill(rect)

    color = UIColor(white: 0.0, alpha: 1.0)
    color.setFill()
    rect = CGRectMake((img!.size.width/2)-50, (img!.size.height/2)-50, 100, 100)
    UIRectFill(rect)

    var maskImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    var maskLayer = CALayer()
    maskLayer.frame = self.imageView.layer.bounds // it'll have the same problem if I set it to self.imageView.layer.frame
    maskLayer.contents = maskImage.CGImage
    maskLayer.contentsGravity = kCAGravityCenter

    self.imageView.image = img
    self.imageView.layer.mask = maskLayer;
    self.imageView.layer.masksToBounds = true
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}
}

I need to know how to align the image mask with the original image. Thank you for your help!

I have good screenshots, but Stackoverflow does not allow me to publish them because I do not have enough reputation!

Answer 1

, , , . , , - , , - , .

, , . , , - , , . , AV Foundation, , , AVMakeRectWithAspectRatioInsideRect ( : https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVFoundation_Functions/index.html#//apple_ref/c/func/AVMakeRectWithAspectRatioInsideRect).

Answer 2

, UIImageView. Subview

!