擦除时图像变得模糊并缩小

Question

我正在使用擦除图像的功能，我的代码如下所示。你可以看到Video HERE。此处current_sticker_img是我的Imageview

注意： 我也使用Pan Gesture缩放图像

 //MARK: Eraser touch event
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        if btn_eraser.isSelected == true || btn_repaint.isSelected == true{
            let touch : UITouch = touches.first!
            lastpoint = touch.location(in: current_sticker_img)
        }
    }
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        if btn_eraser.isSelected == true || btn_repaint.isSelected == true{
            let touch = touches.first!
            let currentPoint : CGPoint = touch.location(in: current_sticker_img)
            let isPointInsideView = current_sticker_img.point(inside: currentPoint, with: event)
            if isPointInsideView
            {
                UIGraphicsBeginImageContext(current_sticker_img.frame.size)
//                UIGraphicsBeginImageContextWithOptions(CGSize(width: (current_sticker_img.image?.size.width)!, height: (current_sticker_img.image?.size.height)!), false, (current_sticker_img.image?.scale)!)

                current_sticker_img
                    .image?.draw(in: CGRect(x: 0, y: 0, width: (current_sticker_img.frame.size.width), height: (current_sticker_img.frame.size.height)))
                UIGraphicsGetCurrentContext()!.setLineCap(.round)
                UIGraphicsGetCurrentContext()?.setLineWidth(Current_slider_value_for_Eraser)

                UIGraphicsGetCurrentContext()?.setShadow(offset: CGSize(width: CGFloat(0), height: CGFloat(0)), blur: 0, color: UIColor.clear.cgColor )
                UIGraphicsGetCurrentContext()!.setBlendMode(.clear)

                UIGraphicsGetCurrentContext()?.move(to: CGPoint(x: CGFloat(lastpoint.x), y: CGFloat(lastpoint.y)))
                UIGraphicsGetCurrentContext()?.addLine(to: CGPoint(x: CGFloat(currentPoint.x), y: CGFloat(currentPoint.y)))
                UIGraphicsGetCurrentContext()!.strokePath()

                current_sticker_img.image = UIGraphicsGetImageFromCurrentImageContext()
                UIGraphicsEndImageContext()
                lastpoint = currentPoint
            }
        }
    }

我做错了什么？请帮帮我。 谢谢