Let's say I have some UIView and also I have a "closed" UIBezierPath inside of that view. What I want to achieve is to have everything "outside" this path be white and inside - transparent (like a hole of that path-shape). Solutions like this don't work, for some reason, part of the shape inside is also white.
You can use the view.layer.mask property to make holes in a a view.
I'm using this piece of code to make mask from images, but you could also just draw you UIBezierPath to CALayer and use that instead.
/*
Get a layer that can be used to mask an image. All pixels with alpha 0 in mask image will be hidden
use as:
self.view.layer.mask = <Mask returned from this call>
self.view.layer.masksToBounds = YES;
*/
+(CALayer*)getMaskLayerFromImage:(UIImage*)image
{
CALayer *mask = [CALayer layer];
mask.contents =(id) image.CGImage;
mask.frame = CGRectMake(0, 0, image.size.width, image.size.height);
return mask;
}
I have achieved this thing by using UIBezierPath and CAShapeLayer
I am taking outlet of view from storyboard.
#IBOutlet weak var myView: UIView!
Create an object of UIBezierPath()
var path = UIBezierPath()
Create a method which take center of view and we create another UIBezierPath() as circlePath which is circle and we append the circle on previous UIBezierPath() path.
Know take a CAShapeLayer and cut the circlePath
Change center point to draw circle on specific point.
func overLay() {
let sizes = CGSize(width: 30, height: 30)
let circlePath = UIBezierPath(ovalIn: CGRect(origin: self.view.center, size: sizes))
path.append(circlePath)
let maskLayer = CAShapeLayer() //create the mask layer
maskLayer.path = path.cgPath // Give the mask layer the path you just draw
maskLayer.fillRule = kCAFillRuleEvenOdd // Cut out the intersection part
myView.layer.mask = maskLayer
}
Related
This question already has answers here:
How can I 'cut' a transparent hole in a UIImage?
(4 answers)
Closed 1 year ago.
I'm trying to avoid CAShapeLayer because I would need to mess with CABasicAnimation, not UIView.animate. So instead, I'm just using UIView's mask property to mask views. Here's my code currently:
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let imageView = UIImageView(frame: CGRect(x: 50, y: 50, width: 200, height: 300))
imageView.image = UIImage(named: "TestImage")
imageView.contentMode = .scaleAspectFill
imageView.clipsToBounds = true
view.addSubview(imageView)
let maskView = UIView(frame: CGRect(x: 100, y: 100, width: 80, height: 80))
maskView.backgroundColor = UIColor.blue /// ensure opaque
maskView.layer.cornerRadius = 10
imageView.mask = maskView /// set the mask
}
}
Without imageView.mask = maskView
With imageView.mask = maskView
It makes a portion of the image view visible. However, this is what I want:
Instead of making part of the image view visible, how can I cut a hole in it?
You can create an image view and set that as your mask. Note that this does not lend itself to animation. If you want to animate the mask to different shapes, you should add a mask to your view's CALayer and use CALayerAnimation, as you mention. It's not that bad.
Below I outline how to generate an image with a transparent part (a hole) that you can use as a mask in an image view. If your goal is to animate the size, shape, or position of the hole, however, this won't work. You'd have to regenerate the mask image for every frame, which would be really slow.
Here's how you would get the effect your are after for static views using an image view as a mask:
Use UIGraphicsBeginImageContextWithOptions() UIGraphicsImageRenderer to create an image that is opaque for most of your image, and has a transparent "hole" where you want a hole.
Then install that image in your image view, and make that image view your mask.
The code to create a mostly opaque image with a transparent rounded rect "hole" might look like this:
/**
Function to create a UIImage that is mostly opaque, with a transparent rounded rect "knockout" in it. Such an image might be used ask a mask
for another view, where the transparent "knockout" appears as a hole in the view that is being masked.
- Parameter size: The size of the image to create
- Parameter transparentRect: The (rounded )rectangle to make transparent in the middle of the image.
- Parameter cornerRadius: The corner radius ot use in the transparent rectangle. Pass 0 to make the rectangle square-cornered.
*/
func imageWithTransparentRoundedRect(size: CGSize, transparentRect: CGRect, cornerRadius: CGFloat) -> UIImage? {
let renderer = UIGraphicsImageRenderer(size: size)
let image = renderer.image { (context) in
let frame = CGRect(origin: .zero, size: size)
UIColor.white.setFill()
context.fill(frame)
let roundedRect = UIBezierPath(roundedRect: transparentRect, cornerRadius: cornerRadius)
context.cgContext.setFillColor(UIColor.clear.cgColor)
context.cgContext.setBlendMode(.clear)
roundedRect.fill()
}
return image
}
And a viewDidLoad method that installs a UIImageView with a mask image view with a hole in it might look like this:
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = .cyan
let size = CGSize(width: 200, height: 300)
let origin = CGPoint(x: 50, y: 50)
let frame = CGRect(origin: origin, size: size)
let imageView = UIImageView(frame: frame)
imageView.image = UIImage(named: "TestImage")
imageView.contentMode = .scaleAspectFill
imageView.clipsToBounds = true
view.addSubview(imageView)
imageView.layer.borderWidth = 2
//Create a mask image view the same size as the (image) view we will be masking
let maskView = UIImageView(frame: imageView.bounds)
//Build an opaque UIImage with a transparent "knockout" rounded rect inside it.
let transparentRect = CGRect(x: 100, y: 100, width: 80, height: 80)
let maskImage = imageWithTransparentRoundedRect(size: size, transparentRect: transparentRect, cornerRadius: 20)
//Install the image with the "hole" into the mask image view
maskView.image = maskImage
//Make the maskView the ImageView's mask
imageView.mask = maskView /// set the mask
}
}
I created a sample project using the code above. You can download it from Github here:
https://github.com/DuncanMC/UIImageMask.git
I just updated the project to also show how to do the same thing using a CAShapeLayer as a mask on the image view's layer. Doing it that way, it's possible to animate changes to the mask layer's path.
The new version has a segmented control that lets you pick whether to mask the image view using a UIImage in the view's mask property, or via a CAShapeLayer used as a mask on the image view's layer.
For the CAShapeLayer version, the mask layer's path is a rectangle the size of the whole image view, with a second, smaller rounded rectangle drawn inside it. The winding rule on the shape layer is then set to the "even/odd" rule, meaning that if you have to cross an even number of shape boundaries to get to a point, it is considered outside the shape. That enables you to create hollow shapes like we need here.
When you select the layer mask option, it enables an animation button that animates random changes to the "cutout" transparent rectangle in the mask.
The function that creates the mask path looks like this:
func maskPath(transparentRect: CGRect, cornerRadius: CGFloat) -> UIBezierPath {
let fullRect = UIBezierPath(rect: maskLayer.frame)
let roundedRect = UIBezierPath(roundedRect: transparentRect, cornerRadius: cornerRadius)
fullRect.append(roundedRect)
return fullRect
}
And the function that does the animation looks like this:
#IBAction func handleAnimateButton(_ sender: Any) {
//Create a CABasicAnimation that will change the path of our maskLayer
//Use the keypath "path". That tells the animation object what property we are animating
let animation = CABasicAnimation(keyPath: "path")
animation.autoreverses = true //Make the animation reverse back to the oringinal position once it's done
//Use ease-in, ease-out timing, which looks smooth
animation.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeInEaseOut)
animation.duration = 0.3 //Make each step in the animation last 0.3 seconds.
let transparentRect: CGRect
//Randomly either animate the transparent rect to a different shape or shift it
if Bool.random() {
//Make the transparent rect taller and skinnier
transparentRect = self.transparentRect.inset(by: UIEdgeInsets(top: -20, left: 20, bottom: -20, right: 20))
} else {
//Shift the transparent rect to by a random amount that still says inside the image view's bounds.
transparentRect = self.transparentRect.offsetBy(dx: CGFloat.random(in: -100...20), dy: CGFloat.random(in: -100...100))
}
let cornerRadius: CGFloat = CGFloat.random(in: 0...30)
//install the new path as the animation's `toValue`. If we dont specify a `fromValue` the animation will start from the current path.
animation.toValue = maskPath(transparentRect: transparentRect, cornerRadius: cornerRadius).cgPath
//add the animation to the maskLayer. Since the animation's `keyPath` is "path",
//it will animate the layer's "path" property to the "toValue"
maskLayer.add(animation, forKey: nil)
//Since we don't actually change the path on the mask layer, the mask will revert to it's original path once the animation completes.
}
The results (using my own sample image) look like this:
A sample of the CALayer based mask animation looks like this:
I wanted to apply a UIEffectView with blur over a tableView but have circular UIImageView objects in each cell show through. I used a mask and adapted the solution from this answer to create a method that would iteratively cut out circles above each cell:
func cutCircle(inView view: UIView, rect1: CGRect, rect2: CGRect?) {
// Create new path and mask
let newMask = CAShapeLayer()
// Create path to clip
let newClipPath = UIBezierPath(rect: view.bounds)
let path1 = UIBezierPath(ovalIn: rect1)
newClipPath.append(path1)
if let rect2 = rect2 {
let path2 = UIBezierPath(ovalIn: rect2)
//FIXME: Need a way to get a union of both paths!
//newClipPath.append(path2)
}
// If view already has a mask
if let originalMask = view.layer.mask, let originalShape = originalMask as? CAShapeLayer, let originalPath = originalShape.path {
// Create bezierpath from original mask's path
let originalBezierPath = UIBezierPath(cgPath: originalPath)
// Append view's bounds to "reset" the mask path before we re-apply the original
newClipPath.append(UIBezierPath(rect: view.bounds))
// Combine new and original paths
newClipPath.append(originalBezierPath)
}
// Apply new mask
newMask.path = newClipPath.cgPath
newMask.fillRule = .evenOdd
view.layer.mask = newMask
}
This function is called on the UIEffectView for each visible tableview cell using: for cell in tableView.visibleCells(). It appends a new circle to the mask.
However, some items have a smaller circle icon overlay, like this:
I added the second CGRect parameter to the method above to conditionally cut out this circle. However, the mask remains intact where the two circles overlap, like this:
I looked at a few answers here, as I needed to find a way to get the union of two UIBezierPath objects. However, this proved very difficult. I don’t think I can use a drawing context as this is a UIEffectView and the mask needs to be cut iteratively.
I tried changing the fill rules (.evenOdd, .nonZero) but this does not have the desired effect.
Are there any tips for combining two overlapping UIBezierPath into a single mask?
The overall aim is to achieve this effect with consecutive tableview cells, but some icons will have the extra circle.
Notice how the bottom icon has the extra circle but it is cropped, and my current technique to cut out this extra circle causes the problem noted above, where the overlap is not masked as expected.
You could use addArcWithCenter method to combine two arcs into desired shape.eg:
#define DEGREES_TO_RADIANS(degrees)((M_PI * degrees)/180)
- (UIBezierPath*)createPath
{
UIBezierPath* path = [[UIBezierPath alloc]init];
[path addArcWithCenter:CGPointMake(25, 25) radius:25 startAngle:DEGREES_TO_RADIANS(30) endAngle:DEGREES_TO_RADIANS(60) clockwise:false];
[path addArcWithCenter:CGPointMake(40, 40) radius:10 startAngle:DEGREES_TO_RADIANS(330) endAngle:DEGREES_TO_RADIANS(120) clockwise:true];
[path closePath];
return path;
}
I wasn't able to find out the exact points but if you could adjust the constants you could create the perfect shape required.
try the following code in your function
let newRect: CGRect
if let rect2 = rect2{
let raw = rect1.union(rect2)
let size = max(raw.width, raw.height)
newRect = CGRect(x: raw.minX, y: raw.minX, width: size, height: size)
}else{
newRect = rect1
}
let path1 = UIBezierPath(ovalIn: newRect)
newClipPath.append(path1)
Full function
func cutCircle(inView view: UIView, rect1: CGRect, rect2: CGRect?) {
// Create new path and mask
let newMask = CAShapeLayer()
// Create path to clip
let newClipPath = UIBezierPath(rect: view.bounds)
let newRect: CGRect
if let rect2 = rect2{
let raw = rect1.union(rect2)
let size = max(raw.width, raw.height) // getting the larger value in order to draw a proper circle
newRect = CGRect(x: raw.minX, y: raw.minX, width: size, height: size)
}else{
newRect = rect1
}
let path1 = UIBezierPath(ovalIn: newRect)
newClipPath.append(path1)
// If view already has a mask
if let originalMask = view.layer.mask, let originalShape = originalMask as? CAShapeLayer, let originalPath = originalShape.path {
// Create bezierpath from original mask's path
let originalBezierPath = UIBezierPath(cgPath: originalPath)
// Append view's bounds to "reset" the mask path before we re-apply the original
newClipPath.append(UIBezierPath(rect: view.bounds))
// Combine new and original paths
newClipPath.append(originalBezierPath)
}
// Apply new mask
newMask.path = newClipPath.cgPath
newMask.fillRule = .evenOdd
view.layer.mask = newMask
}
I used the built-in function union to create a raw CGRect and then I get the max value to draw a proper circle.
Thanks to the accepted answer (from user Tibin Thomas) I was able to adapt the use of arcs with UIBezierPath to obtain exactly what I needed. I have accepted his answer but posted my final code here for future reference.
Of note, before calling this method, I have to convert the CGRect coordinates from the UIImageViews superview to the coordinate space of my UIEffectView. I also apply an inset of -1 to obtain the 1pt border. Thus the radii used are 1 greater than the radii of my UIImageViews.
func cutCircle(inView view: UIView, rect1: CGRect, rect2: CGRect?) {
// Create new path and mask
let newMask = CAShapeLayer()
// Create path to clip
let newClipPath = UIBezierPath(rect: view.bounds)
// Center of rect1
let x1 = rect1.midX
let y1 = rect1.midY
let center1 = CGPoint(x: x1, y: y1)
// New path
let newPath: UIBezierPath
if let rect2 = rect2 {
// Need to get two arcs - main icon and padlock icon
// Center of rect2
let x2 = rect2.midX
let y2 = rect2.midY
let center2 = CGPoint(x: x2, y: y2)
// These values are hard-coded for 25pt radius main icon and bottom-right-aligned 10pt radius padlock icon with a 1pt additional border
newPath = UIBezierPath(arcCenter: center1, radius: 26, startAngle: 1.2, endAngle: 0.3, clockwise: true)
newPath.addArc(withCenter: center2, radius: 11, startAngle: 5.8, endAngle: 2.2, clockwise: true)
} else {
// Only single circle is needed
newPath = UIBezierPath(ovalIn: rect1)
}
newPath.close()
newClipPath.append(newPath)
// If view already has a mask
if let originalMask = view.layer.mask,
let originalShape = originalMask as? CAShapeLayer,
let originalPath = originalShape.path {
// Create bezierpath from original mask's path
let originalBezierPath = UIBezierPath(cgPath: originalPath)
// Append view's bounds to "reset" the mask path before we re-apply the original
newClipPath.append(UIBezierPath(rect: view.bounds))
// Combine new and original paths
newClipPath.append(originalBezierPath)
}
// Apply new mask
newMask.path = newClipPath.cgPath
newMask.fillRule = .evenOdd
view.layer.mask = newMask
}
I have a question about how to apply multiple masks to a UIView that already has a mask.
The situation:
I have a view with an active mask that creates a hole in its top left corner, this is a template UIView that is reused everywhere in the project. Later in the project I would like to be able to create a second hole but this time in the bottom right corner, this without the need to create a completely new UIView.
The problem:
When I apply the bottom mask, it of course replaces the first one thus removing the top hole ... Is there a way to combine them both? And for that matter to combine any existing mask with a new one?
Thank you in advance!
Based on #Sharad's answer, I realised that re-adding the view's rect would enable me to combine the original and new mask into one.
Here is my solution:
func cutCircle(inView view: UIView, withRect rect: CGRect) {
// Create new path and mask
let newMask = CAShapeLayer()
let newPath = UIBezierPath(ovalIn: rect)
// Create path to clip
let newClipPath = UIBezierPath(rect: view.bounds)
newClipPath.append(newPath)
// If view already has a mask
if let originalMask = view.layer.mask,
let originalShape = originalMask as? CAShapeLayer,
let originalPath = originalShape.path {
// Create bezierpath from original mask's path
let originalBezierPath = UIBezierPath(cgPath: originalPath)
// Append view's bounds to "reset" the mask path before we re-apply the original
newClipPath.append(UIBezierPath(rect: view.bounds))
// Combine new and original paths
newClipPath.append(originalBezierPath)
}
// Apply new mask
newMask.path = newClipPath.cgPath
newMask.fillRule = kCAFillRuleEvenOdd
view.layer.mask = newMask
}
This is code I have used in my project to create one circle and one rectangle mask in UIView, you can replace the UIBezierPath line with same arc code :
func createCircleMask(view: UIView, x: CGFloat, y: CGFloat, radius: CGFloat, downloadRect: CGRect){
self.layer.sublayers?.forEach { ($0 as? CAShapeLayer)?.removeFromSuperlayer() }
let mutablePath = CGMutablePath()
mutablePath.addArc(center: CGPoint(x: x, y: y + radius), radius: radius, startAngle: 0.0, endAngle: 2 * 3.14, clockwise: false)
mutablePath.addRect(view.bounds)
let path = UIBezierPath(roundedRect: downloadRect, byRoundingCorners: [.topLeft, .bottomRight], cornerRadii: CGSize(width: 5, height: 5))
mutablePath.addPath(path.cgPath)
let mask = CAShapeLayer()
mask.path = mutablePath
mask.fillRule = kCAFillRuleEvenOdd
mask.backgroundColor = UIColor.clear.cgColor
view.layer.mask = mask
}
Pass your same UIView, it removes previous layers and applies new masks on same UIView.
Here mask.fillRule = kCAFillRuleEvenOdd is important. If you notice there are 3 mutablePath.addPath() functions, what kCAFillRuleEvenOdd does is, it first creates a hole with the arc then adds Rect of that view's bound and then another mask to create 2nd hole.
You can do something like the following, if you don't only have "simple shapes" but actual layers from e.g. other views, like UILabel or UIImageView.
let maskLayer = CALayer()
maskLayer.frame = viewToBeMasked.bounds
maskLayer.addSublayer(self.imageView.layer)
maskLayer.addSublayer(self.label.layer)
viewToBeMasked.bounds.layer.mask = maskLayer
So basically I just create a maskLayer, that contains all the other view's layer as sublayer and then use this as a mask.
I need to add the camera layer on any irregular shaped image i.e. lets say i have a image which is having irregular shape and inside image there is a circular or any other irregular shape in which i want to embed the live camera.
Any idea how i can achieve this functionality?
You can use UIBezierPath to draw irregular share for a mask CAShapeLayer
let size = 200.0
Create a CAShapeLayer and draw shape in which you wanna embed a cameraPreviewLayer.
let maskLayer = CAShapeLayer()
let maskPath = UIBezierPath()
maskPath.move(to: .zero)
maskPath.addLine(to: CGPoint(x: 10, y: -size))
maskPath.addLine(to: CGPoint(x: size/2, y: -size))
maskPath.addLine(to: CGPoint(x: size*2, y: size))
maskPath.close()
maskLayer.anchorPoint = .zero
Set the mask positon
maskLayer.position = CGPoint(x: 100, y: 400)
maskLayer.path = maskPath.cgPath
self.yourVideoPreviewLayer.mask = maskLayer
self.yourVideoPreviewLayer.masksToBounds = true
Or you can make an image with a shape in which you wanna embed a cameraPreviewLayer. Or if your image's inner shape have an alpha value = 0 you can reverse alpha of your original image and use it as a mask.
let maskLayer = CAShapeLayer()
maskLayer.anchorPoint = .zero
maskLayer.frame = videoPreviewLayer.bounds
maskLayer.contents = YourReversedImage.cgImage
self.videoPreviewLayer.mask = maskLayer
self.videoPreviewLayer.masksToBounds = true
Add additional UIView upon of your UIImageView with same frames(width, height and position). it shouldn't be a subview of UIImageView!
Set background of this UIView to clearColor and create whatever layer you want.
Now you can use this layer as AVCaptureVideoPreviewLayer instead of using UIImageView layers
I want to know how to simply mask the visible area of a UIView of any kind. All the answers/tutorials I've read so far describe masking with an image, gradient or creating round corners which is way more advanced than what I am after.
Example: I have a UIView with the bounds (0, 0, 100, 100) and I want to cut away the right half of the view using a mask. Therefore my mask frame would be (0, 0, 50, 100).
Any idea how to do this simply? I don't want to override the drawrect method since this should be applicable to any UIView.
I've tried this but it just makes the whole view invisible.
CGRect mask = CGRectMake(0, 0, 50, 100);
UIView *maskView = [[UIView alloc] initWithFrame:mask];
viewToMask.layer.mask = maskView.layer;
Thanks to the link from MSK, this is the way I went with which works well:
// Create a mask layer and the frame to determine what will be visible in the view.
CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
CGRect maskRect = CGRectMake(0, 0, 50, 100);
// Create a path with the rectangle in it.
CGPathRef path = CGPathCreateWithRect(maskRect, NULL);
// Set the path to the mask layer.
maskLayer.path = path;
// Release the path since it's not covered by ARC.
CGPathRelease(path);
// Set the mask of the view.
viewToMask.layer.mask = maskLayer;
Thanks for answers guys.
In case someone can't find suitable answer on SO for this question for hours, like i just did, i've assembled a working gist in Swift 2.2 for masking/clipping UIView with CGRect/UIBezierPath:
https://gist.github.com/Flar49/7e977e81f1d2827f5fcd5c6c6a3c3d94
extension UIView {
func mask(withRect rect: CGRect, inverse: Bool = false) {
let path = UIBezierPath(rect: rect)
let maskLayer = CAShapeLayer()
if inverse {
path.append(UIBezierPath(rect: self.bounds))
maskLayer.fillRule = kCAFillRuleEvenOdd
}
maskLayer.path = path.cgPath
self.layer.mask = maskLayer
}
func mask(withPath path: UIBezierPath, inverse: Bool = false) {
let path = path
let maskLayer = CAShapeLayer()
if inverse {
path.append(UIBezierPath(rect: self.bounds))
maskLayer.fillRule = kCAFillRuleEvenOdd
}
maskLayer.path = path.cgPath
self.layer.mask = maskLayer
}
}
Usage:
let viewSize = targetView.bounds.size
let rect = CGRect(x: 20, y: 20, width: viewSize.width - 20*2, height: viewSize.height - 20*2)
// Cuts rectangle inside view, leaving 20pt borders around
targetView.mask(withRect: rect, inverse: true)
// Cuts 20pt borders around the view, keeping part inside rect intact
targetView.mask(withRect: rect)
Hope it will save someone some time in the future :)
No need any mask at all.
Just put it into a wrapper view with the smaller frame, and set clipsToBounds.
wrapper.clipsToBounds = true
Very simple example in a Swift ViewController, based on the accepted answer:
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let redView = UIView(frame: view.bounds)
view.addSubview(redView)
view.backgroundColor = UIColor.green
redView.backgroundColor = UIColor.red
mask(redView, maskRect: CGRect(x: 50, y: 50, width: 50, height: 50))
}
func mask(_ viewToMask: UIView, maskRect: CGRect) {
let maskLayer = CAShapeLayer()
let path = CGPath(rect: maskRect, transform: nil)
maskLayer.path = path
// Set the mask of the view.
viewToMask.layer.mask = maskLayer
}
}
Output
An optional layer whose alpha channel is used as a mask to select
between the layer's background and the result of compositing the
layer's contents with its filtered background.
#property(retain) CALayer *mask
The correct way to do what you want is to create the maskView of the same frame (0, 0, 100, 100) as the viewToMask which layer you want to mask. Then you need to set the clearColor for the path you want to make invisible (this will block the view interaction over the path so be careful with the view hierarchy).
Swift 5 , thanks #Dan Rosenstark
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let red = UIView(frame: view.bounds)
view.addSubview(red)
view.backgroundColor = UIColor.cyan
red.backgroundColor = UIColor.red
red.mask(CGRect(x: 50, y: 50, width: 50, height: 50))
}
}
extension UIView{
func mask(_ rect: CGRect){
let mask = CAShapeLayer()
let path = CGPath(rect: rect, transform: nil)
mask.path = path
// Set the mask of the view.
layer.mask = mask
}
}
Setting MaskToBounds is not enough, for example, in scenario where you have UIImageView that is positioned inside RelativeLayout. In case that you put your UIImageView to be near top edge of the layout and then you rotate your UIImageView, it will go over layout and it won't be cropped. If you set that flag to true, it will be cropped yes, but it will also be cropped if UIImageView is on the center of layout, and that is not what you want.
So, determinating maskRect is the right approach.