如何在 Swift 中将多个重叠的 UIImage 组合成一个 UIImage？

Question

I am creating an app where users can choose from a collection of images (multiple) and add the chosen image to a chosen background. They should then be able to save the image, so I need help merging all the images into one to be saved.

The ViewController has a large UIImageView which serves as the background. When the user selects an image to add, the image is added to the UIImageView as a subview.

//chosenImage is a UIImageView with an chosen image
backgroundImageView.addSubView(chosenImage)

I need to save the image as the size of the backgroundView with the overlaid images.

How can I achieve this?

I have searched around but only found Obj-C answers and some that don't work.

For those looking for the same answer this is what you do to save the image on button press:

@IBAction func saveImage(sender: AnyObject) {

    let snapShot:UIView = backgroundImage.snapshotViewAfterScreenUpdates(true)

    UIGraphicsBeginImageContext(backgroundImage.bounds.size)

    snapShot.drawViewHierarchyInRect(backgroundImage.bounds, afterScreenUpdates: true)

    let image:UIImage = UIGraphicsGetImageFromCurrentImageContext()

    UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)


}

Answer 1

I need to save the image as the size of the backgroundView with the overlaid images.

You have two choices. One is to draw a composite image in code, just drawing the images, positioned as they are by the image view and its subviews, into an image graphics context. In your case, though, a simpler approach would be simply to render or snapshot the image view: that will effectively be a screen shot of the image view and its subviews, which is exactly what the user is seeing.