如何在 Swift 中的动态相机视图上方添加具有自定义形状的模糊蒙版？

Question

我正在使用 Swift 开发具有相机功能的 iOS 应用程序，它需要在相机视图上方有一个模糊层，中间有一个孔，如下图所示。

我尝试了几种方法，但都没有在不覆盖孔的情况下添加模糊效果。在 Google 上花费时间后，我也没有找到可行的解决方案。

谁能提供一些关于如何仅模糊附加到图像视图的 png 图像的非透明部分的提示？

我尝试过的方法：

1. 使用 iOS 8 内置的模糊效果

   let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Dark)
   let blurEffectView = UIVisualEffectView(effect: blurEffect)
   maskImage.addSubview(blurEffectView)
   

2. 使用“CIGaussianBlur”滤镜

   var imageToBlur = CIImage(image: image)
   var blurfilter = CIFilter(name: "CIGaussianBlur")
   blurfilter.setValue(imageToBlur, forKey: "inputImage")
   var resultImage = blurfilter.valueForKey("outputImage") as! CIImage
   var blurredImage = UIImage(CIImage: resultImage)
   self.maskImage.image = blurredImage
   

我想要的视觉效果：

Answer 1

我通过创建一个带有所述模糊图像的图层的叠加层来做到这一点，然后使用一个蒙版，该蒙版是从一条一直围绕范围的路径构建的，然后跳到切口孔，去与缠绕填充规则方向相反。

请参阅此处的文档：

https://developer.apple.com/library/ios/documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_paths/dq_paths.html

尽管有很多记录在案的例子，这里有一个： drawing with clear color on UIView (cutting a hole) in static method

Answer 2

在图像中的某个圆形区域外应用模糊的最简单方法是应用高斯模糊和渐变蒙版。 HereApple 上面有帖子。

执行此操作的基本常见步骤：

1. 使用 CIRadialGradient 创建蒙版滤镜（在此处调整圆心）

   guard let radialMask = CIFilter(name:"CIRadialGradient") else {
      return nil
   }
   
   let h = inputImage.extent.size.height
   let w = inputImage.extent.size.width
   
   // Adjust your circular hole position here
   let imageCenter = CIVector(x:0.55 * w, y:0.6 * h)
   radialMask.setValue(imageCenter, forKey:kCIInputCenterKey)
   // Small fraction of the image's dimension (high sharp)
   radialMask.setValue(0.2 * h, forKey:"inputRadius0")
   // Large fraction of the image's dimension (lower sharp)
   radialMask.setValue(0.3 * h, forKey:"inputRadius1")
   radialMask.setValue(CIColor(red:0, green:1, blue:0, alpha:0), 
                       forKey:"inputColor0")
   radialMask.setValue(CIColor(red:0, green:1, blue:0, alpha:1), 
                       forKey:"inputColor1")
   

2. 创建 CIMaskedVariableBlur 来掩盖模糊区域

   guard let maskedVariableBlur = CIFilter(name:"CIMaskedVariableBlur") else {
      return nil
   }
   // inputImage:- Your original image
   maskedVariableBlur.setValue(inputImage, forKey: kCIInputImageKey)
   // inputRadiusKey:- Right degree of blur desired
   maskedVariableBlur.setValue(10, forKey: kCIInputRadiusKey)
   // here we will use result of radialMask filter result image
   maskedVariableBlur.setValue(radialMask.outputImage, forKey: "inputMask")
   // Get result image
   let selectivelyFocusedCIImage = maskedVariableBlur.outputImage
   // Convert your result image to UIImage
   let resultImage = UIImage(ciImage: selectivelyFocusedCIImage)
   

额外：- 你可以使用UIPanGestureRecognizer 来移动你的圆孔

1- 创建手势识别器：

lazy var panGesture: UIPanGestureRecognizer = {
    let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handleDrag))
    return panGesture
}()

2- 将手势识别器添加到您的图像视图

self.imageView.isUserInteractionEnabled = true
self.imageView.addGestureRecognizer(panGesture)

3- 处理你的手势

var initialCenter = CGPoint()
@objc fileprivate func handleDrag(_ gestureRecognizer: UIPanGestureRecognizer) {
  guard gestureRecognizer.view != nil else {return}

  let translation = gestureRecognizer.translation(in: imageView.superview)

  if gestureRecognizer.state == .began {
      // Save the view's original position.
      self.initialCenter = CGPoint(x: centerVector.x, y: centerVector.y)
  }
  // Update the position for the .began, .changed, and .ended states
  if gestureRecognizer.state != .cancelled {
      // Add the X and Y translation to the view's original position.
      let newCenter = CGPoint(x: initialCenter.x + translation.x, y: initialCenter.y + -translation.y)
    
    
      self.imageCenter = CIVector.init(cgPoint: newCenter)
      // Then apply your filter on gestureRecognizer.state == .end
    
  } else {
      // On cancellation, return the piece to its original location.
      self.imageCenter = CIVector(x: initialCenter.x, y: initialCenter.y)
  }
}