Capture visible portion of UIScrollView and subview - iphone

Question

I have zoomable image in a UIScrollview. Once the image is scrolled to the user's liking, the scrollview is locked. A UITextField can then be edited, and is (currently) added to the UIImageView. The context of the image is captured and saved.
Without scrolling, this works fine, however, the context is based on the frame of the UIImageView. How can it capture the visible portion of the screen instead, leaving out the navigation bar and toolbar? The function used to save the image is below.
#IBAction func saveButtonPressed(sender: AnyObject) {
let newImage = imageStore.createImage(textLabelBottom.text, imageName: "image1") { () -> UIImage in
// Can't add the textLabel to imageView because its size changes
self.imageView.addSubview(self.textLabelBottom)
UIGraphicsBeginImageContextWithOptions(self.imageView.frame.size, false, 0.0)
let ctx = UIGraphicsGetCurrentContext()
self.imageView.layer.renderInContext(ctx)
self.imageToSave = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return self.imageToSave
}
imageStore.saveImage(newImage)
self.showActivityViewController()
}
I wan't to save the visible portion of the image based on its position in the scrollview with the textLabel in a static spot. The code currently adds textLabel to the same point in the image regardless of zoom, with the saved image either very small or very large based on the UIScrollView.
Update: I changed the code to the following:
#IBAction func saveButtonPressed(sender: AnyObject) {
let newImage = imageStore.createImage(textLabelBottom.text, imageName: "image1") { () -> UIImage in
// Can't add the textLabel to imageView because its size changes
self.imageView.addSubview(self.textLabelBottom)
UIGraphicsBeginImageContextWithOptions(self.imageScrollView.bounds.size, false, UIScreen.mainScreen().scale)
let ctx = UIGraphicsGetCurrentContext()
let offset: CGPoint = self.imageScrollView.contentOffset
CGContextTranslateCTM(UIGraphicsGetCurrentContext(), -offset.x, -offset.y)
self.imageScrollView.layer.renderInContext(ctx)
self.imageToSave = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return self.imageToSave
}
imageStore.saveImage(newImage)
self.showActivityViewController()
}
This works properly, but the text field is obviously out of place. Do I add it to a specific CGPoint within the context?
Update 2:
It's my understanding that CGContextTranslateCTM changes the coordinate system to that of the layer you're working on. In this case, the new {0, 0} would be at the offset of the scrollview. When I want to place my textfield into the context, though, it doesn't show up in the right place (offscreen). Trying something like this:
#IBAction func saveButtonPressed(sender: AnyObject) {
let newImage = imageStore.createImage(textLabelBottom.text, imageName: "image1") { () -> UIImage in
// Can't add the textLabel to imageView because its size changes
self.imageView.addSubview(self.textLabelBottom)
UIGraphicsBeginImageContextWithOptions(self.imageScrollView.bounds.size, false, UIScreen.mainScreen().scale)
let ctx = UIGraphicsGetCurrentContext()
let offset: CGPoint = self.imageScrollView.contentOffset
CGContextTranslateCTM(UIGraphicsGetCurrentContext(), -offset.x, -offset.y)
self.imageScrollView.layer.renderInContext(ctx)
//Move to the correct point and render
CGContextMoveToPoint(ctx, /*point1*/, /*point2*/)
self.textLabelBottom.layer.renderInContext(ctx)
self.imageToSave = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return self.imageToSave
}
imageStore.saveImage(newImage)
self.showActivityViewController()
}
What else do I need to do to the context to do this properly?