iOS MachineLearning 系列（9）—— 人物蒙版图生成
人物蒙版图能力是Vision框架在iOS 15中新增的功能，这个功能可以将图片中的人物按照轮廓生成无光蒙版。无光蒙版在实际业务中非常有用，使用此蒙版可以方便的将人物从图片中提取出来，然后和其他的背景图进行合成。
1 - 人物蒙版的提取
首先，人物蒙版的提取非常简单，使用VNGeneratePersonSegmentationRequest创建蒙版分析请求，如下：
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| private lazy var personRequest: VNGeneratePersonSegmentationRequest = {
let request = VNGeneratePersonSegmentationRequest { request, error in
DispatchQueue.main.async {
self.drawTask(request: request as! VNGeneratePersonSegmentationRequest)
}
}
return request
}()
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使用VNImageRequestHandler来触发请求即可：
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let image = UIImage(named: "image7")!
lazy var imageRequestHandler = VNImageRequestHandler(ciImage: CIImage(cgImage: image.cgImage!),
orientation: .up,
options: [:])
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请求的结果VNPixelBufferObservation中会封装蒙版图片CVPixelBuffer数据，如下：
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| open class VNPixelBufferObservation : VNObservation {
open var pixelBuffer: CVPixelBuffer { get }
open var featureName: String? { get }
}
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处理请求结果如下：
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| private func drawTask(request: VNGeneratePersonSegmentationRequest) {
for result in request.results ?? [] {
// 创建CIImage实例
let ciImage = CIImage(cvPixelBuffer: result.pixelBuffer)
// 默认返回的蒙版为黑白两色，这里讲所有黑色替换成透明色
let filter = CIFilter(name: "CIMaskToAlpha", parameters: [kCIInputImageKey: ciImage])
guard let outputImage = filter?.outputImage else { return }
let context = CIContext(options: nil)
let cgImage = context.createCGImage(outputImage, from: outputImage.extent)
let uiImage = UIImage(cgImage: cgImage!)
let v = UIImageView(image: uiImage)
v.frame = imageView.frame
v.backgroundColor = .black
v.frame.origin.y += imageView.frame.height
v.image = uiImage
view.addSubview(v)
}
}
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效果如下图：
2 - 进行人物提取
获取到了蒙版，提取人物将很简单，修改上述代码如下：
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| private func drawTask(request: VNGeneratePersonSegmentationRequest) {
for result in request.results ?? [] {
print(result.pixelBuffer)
let ciImage = CIImage(cvPixelBuffer: result.pixelBuffer)
let filter = CIFilter(name: "CIMaskToAlpha", parameters: [kCIInputImageKey: ciImage])
guard let outputImage = filter?.outputImage else { return }
let context = CIContext(options: nil)
let cgImage = context.createCGImage(outputImage, from: outputImage.extent)
let uiImage = UIImage(cgImage: cgImage!)
let v = UIImageView(image: uiImage)
v.frame = imageView.frame
v.backgroundColor = .blue
v.frame.origin.y += imageView.frame.height
v.image = uiImage
view.addSubview(v)
let v2 = UIImageView(image: image)
v2.frame = v.frame
v2.frame.origin.y += v.frame.height
let mask = UIImageView(image: uiImage)
mask.frame = CGRect(x: 0, y: 0, width: v2.frame.size.width, height: v2.frame.size.height)
mask.backgroundColor = .clear
v2.mask = mask
view.addSubview(v2)
}
}
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效果如下：
完整的示例代码可以在如下地址找到：
https://github.com/ZYHshao/MachineLearnDemo
VNGeneratePersonSegmentationRequest结合CIFilter的使用，可以方便的进行背景合成。
