截取圖片、合併圖片

//截取圖片
func handleImage(flipView:RectFlipAlphaView) -> UIImage {
      let rect = CGRect(x: flipView.frame.origin.x - self.frame.origin.x, y: flipView.frame.origin.y - self.frame.origin.y, width: flipView.frame.size.width, height: flipView.frame.size.height)
  //標準是不是應該用guard
     if let CGImage = CGImageCreateWithImageInRect(self.image?.CGImage, rect) {
     //這裏也可以使用UIImage(CGImage: CGImage)方法來生成新的圖片
           let image = UIImage(CGImage: CGImage, scale: viewScale, orientation: self.image!.imageOrientation) as UIImage
           return image
      }else {
          return UIImage()
      }
}

//合併圖片
let rect = CGRect(x: rectView.frame.origin.x - board.frame.origin.x, y: rectView.frame.origin.y - board.frame.origin.y, width: rectView.frame.size.width, height: rectView.frame.size.height)

let flipImage = rectView.imageView.image    

UIGraphicsBeginImageContext(image.size)

// Draw image1
image.drawInRect(CGRectMake(0, 0,image.size.width, image.size.height))
// Draw image2
flipImage!.drawInRect(rect)

let resultingImage = UIGraphicsGetImageFromCurrentImageContext()

UIGraphicsEndImageContext()