UIImage from UIView image capture keeps crashing? Swift iOS9

Question

This is an odd issue because sometimes the code works fine and others times it crashes. But lately it's only been crashing.

I have an image that I'm getting from a uiview. I grab the image using the capture function below then send the image to a property to go to prepareForSegue to be sent to the next view controller. The code keeps crashing when it's time to return the image. I debugged it and saw the property definitely went from nil to containing the image however when it's time to segue it crashes. But the crash is within the capture function not the segue. It's weird because the image is returned (debugger showed it) but the capture return is where the crash keeps happening. The crash happens on:

//This seems to be the main problem
return capturedImage

and here's the crash log for the returned capturedImage

Thread1: EXC_BAD_INSTRUCTION (code=EXC_1336_INVOP, subcode=0x0)

I was also getting crashes on this line but somehow the crashes stopped. I can't put a crash log for this one because it stopped crashing but I don't know why or how it stopped

view!.layer.renderInContext(UIGraphicsGetCurrentContext()!)

Any ideas?

Btw I use a storyboard button to trigger the segue.

class MainController: UIViewController {

@IBOutlet weak var mainView: UIView!

var mainPic: UIImage? 


override func viewDidLoad() {
        super.viewDidLoad()
}

//MARK: -Func to convert image in uiview to uiimage
//get image from UIView, render it for Retina compatibility, then return it as an UIImage
func captureAndRenderUIImageFromUIView(view:UIView?) -> UIImage {

    UIGraphicsBeginImageContextWithOptions((view?.bounds.size)!, true, 0.0)
    view!.drawViewHierarchyInRect(view!.bounds, afterScreenUpdates: true)

    //I was also getting crashes on this line but they stopped??
    view!.layer.renderInContext(UIGraphicsGetCurrentContext()!)
    let capuredImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    //The return value is where the crash keeps happening
    return capturedImage
}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

     self.mainPic = self.captureAndRenderUIImageFromUIView(mainView)

     if segue.identifier == "toDetailController"{

     let detailVC = segue.destinationViewController as! DetailController
     detailVC.detailPic = self.mainPic!
    }
 }

}

}

Here's the view it's going to

class DetailController: UIViewController {
@IBOutlet weak var imageView: UIImageView!

var detailPic: UIImage? 

override func viewDidLoad() {
     super.viewDidLoad()
     self.imageView.image = self.detailPic
   }

}

Answer 1

Hi there: I started out trying to do things in much the same way you've tried to here; however, it is error prone and unstable. I recently discovered that you can save yourself a lot of hassle by using the UIView method snapshotViewAfterScreenUpdates. Simply call this directly on the view you want to take a snapshot of and it will return a UIImage.

You can see more detail at: https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIView_Class/#//apple_ref/occ/instm/UIView/snapshotViewAfterScreenUpdates:

In fact I've learned something here too as there appears to be a family of these functions (e.g. a function which gives you a resizeable UIImageView).

Hope that helps.

EDIT: In one of my apps I implemented this through a subroutine as follows:

func getSnapshot(target: UIView) -> Void {
            // Clean down
            if let _ = self.snapshotView where self.snapshotView.isDescendantOfView(self) {
                self.snapshotView.removeFromSuperview()
            }

            self.snapshotView = target.snapshotViewAfterScreenUpdates(true)
            let snapshotFrame : CGRect = CGRect(origin: recognizer.locationInView(self), size: target.frame.size)
            self.snapshotView.frame = snapshotFrame
            self.addSubview(self.snapshotView)

            self.canMoveSnapshot = true
        }