Ios 将vImage_标尺与KCVPIXELFORMATTYPE420YPCBCCR8BIPLANARVIDEAGE一起使用

我从iPhone的前摄像头接收到一个

CMSampleBuffer

。目前它的大小是1920x1080，我想把它缩小到1280x720。我想使用vImageScale函数，但无法使其正常工作。相机的像素格式是

kCVPixelFormatTypeƤYPCBCCR8BIPLANARVIDEORAGE

，因此我尝试了以下操作，但它输出了一个奇怪的绿色图像，但不正确：

private var scaleBuffer: vImage_Buffer = {
  var scaleBuffer: vImage_Buffer = vImage_Buffer()
  let newHeight = 720
  let newWidth = 1280
  scaleBuffer.data = UnsafeMutableRawPointer.allocate(byteCount: Int(newWidth * newHeight * 4), alignment: MemoryLayout<UInt>.size)
  scaleBuffer.width = vImagePixelCount(newWidth)
  scaleBuffer.height = vImagePixelCount(newHeight)
  scaleBuffer.rowBytes = Int(newWidth * 4)
  return scaleBuffer
}()

func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection)
    {

  guard let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else {
    return
  }

  CVPixelBufferLockBaseAddress(imageBuffer, CVPixelBufferLockFlags(rawValue: 0))

  // create vImage_Buffer out of CVImageBuffer
  var inBuff: vImage_Buffer = vImage_Buffer()
  inBuff.width = UInt(CVPixelBufferGetWidth(imageBuffer))
  inBuff.height = UInt(CVPixelBufferGetHeight(imageBuffer))
  inBuff.rowBytes = CVPixelBufferGetBytesPerRow(imageBuffer)
  inBuff.data = CVPixelBufferGetBaseAddress(imageBuffer)

  // perform scale
  var err = vImageScale_CbCr8(&inBuff, &scaleBuffer, nil, 0)
  if err != kvImageNoError {
      print("Can't scale a buffer")
      return
  }
  CVPixelBufferUnlockBaseAddress(imageBuffer, CVPixelBufferLockFlags(rawValue: 0))

  var newBuffer: CVPixelBuffer?
  let attributes : [NSObject:AnyObject] = [
    kCVPixelBufferCGImageCompatibilityKey : true as AnyObject,
    kCVPixelBufferCGBitmapContextCompatibilityKey : true as AnyObject
  ]

  let status = CVPixelBufferCreateWithBytes(kCFAllocatorDefault,
                                                  Int(scaleBuffer.width), Int(scaleBuffer.height),
                                                  kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange, scaleBuffer.data,
                                                  Int(scaleBuffer.width) * 4,
                                                  nil, nil,
                                                  attributes as CFDictionary?, &newBuffer)

  guard status == kCVReturnSuccess,
        let b = newBuffer else {
    return
  }

  // Do something with the buffer to output it
}

private var scaleBuffer:vImage\u Buffer={
变量scaleBuffer:vImage_Buffer=vImage_Buffer（）
设newHeight=720
设newWidth=1280
scaleBuffer.data=unsafemeutablerawpointer.allocate（字节数：Int（newWidth*newHeight*4），对齐方式：MemoryLayout.size）
scaleBuffer.width=vImagePixelCount（新宽度）
scaleBuffer.height=vImagePixelCount（新高度）
scaleBuffer.rowBytes=Int（新宽度*4）
返回刻度缓冲器
}()
func captureOutput（\uOutput:AVCaptureOutput，didOutput sampleBuffer:CMSampleBuffer，from connection:AVCaptureConnection）
{
guard let imageBuffer=CMSampleBufferGetImageBuffer（sampleBuffer）else{
返回
}
CVPixelBufferLockBaseAddress（imageBuffer，CVPixelBufferLockFlags（rawValue:0））
//从CVImageBuffer中创建vImage_缓冲区
变量inBuff:vImage_Buffer=vImage_Buffer（）
inBuff.width=UInt（CVPixelBufferGetWidth（imageBuffer））
inBuff.height=UInt（CVPixelBufferGetHeight（imageBuffer））
inBuff.rowBytes=CVPixelBufferGetBytesPerRow（图像缓冲区）
inBuff.data=CVPixelBufferGetBaseAddress（imageBuffer）
//表演规模
var err=vImageScale_CbCr8（&inBuff，&scaleBuffer，零，0）
如果错误！=kvImageNoError{
打印（“无法缩放缓冲区”）
返回
}
CVPixelBufferUnlockBaseAddress（imageBuffer，CVPixelBufferLockFlags（rawValue:0））
var newBuffer:CVPixelBuffer？
let属性：[NSObject:AnyObject]=[
kCVPixelBufferCGImageCompatibilityKey:与任何对象一样为true，
kCVPixelBufferCGBitmapContextCompatibilityKey:与任何对象一样为true
]
let status=CVPixelBufferCreateWithBytes（kCFAllocatorDefault，
Int（缩放缓冲宽度），Int（缩放缓冲高度），
kCVPixelFormatTypeƤYPCBCRC8BIPLANARVIDERANGE，scaleBuffer.data，
整数（刻度缓冲宽度）*4，
零,零,，
属性为CFDictionary？，&newBuffer）
防护状态==kCVReturnSuccess，
设b=newBuffer-else{
返回
}
//对缓冲区执行一些操作以输出它
}

这里怎么了？看看这个答案，看起来我需要分别缩放“Y”和“UV”平面。我如何在swift中实现这一点，然后将它们合并回一个CVPixelBuffer