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我CMSampleBuffer收到了来自我的 iPhone 相机的信息。它是 1920x1080 像素，但我希望它是 1280x720 像素。我有以下代码来执行此操作：

private var yScaleBuffer: vImage_Buffer = {
  var scaleBuffer: vImage_Buffer = vImage_Buffer()
  let newHeight = 720
  let newWidth = 1280
  scaleBuffer.data = UnsafeMutableRawPointer.allocate(byteCount: Int(newWidth * newHeight * 8), alignment: MemoryLayout<UInt>.size)
  scaleBuffer.width = vImagePixelCount(newWidth)
  scaleBuffer.height = vImagePixelCount(newHeight)
  scaleBuffer.rowBytes = Int(newWidth * 8)
  return scaleBuffer
}()

private var uvScaleBuffer: vImage_Buffer = {
  var scaleBuffer: vImage_Buffer = vImage_Buffer()
  let newHeight = 720
  let newWidth = 1280
  scaleBuffer.data = UnsafeMutableRawPointer.allocate(byteCount: Int(newWidth * newHeight * 8), alignment: MemoryLayout<UInt>.size)
  scaleBuffer.width = vImagePixelCount(newWidth)
  scaleBuffer.height = vImagePixelCount(newHeight)
  scaleBuffer.rowBytes = Int(newWidth * 8)
  return scaleBuffer
}()


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

  guard let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else {
    print("Error acquiring sample buffer")
    return
  }

  CVPixelBufferLockBaseAddress(imageBuffer, CVPixelBufferLockFlags(rawValue: 0))

  // create vImage_Buffer out of CVImageBuffer
  var yInBuff: vImage_Buffer = vImage_Buffer()
  yInBuff.width = UInt(CVPixelBufferGetWidth(imageBuffer))
  yInBuff.height = UInt(CVPixelBufferGetHeight(imageBuffer))
  yInBuff.rowBytes = CVPixelBufferGetBytesPerRow(imageBuffer)
  yInBuff.data = CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0)

  // perform scale of Y plane
  let yError = vImageScale_Planar8(&yInBuff, &yScaleBuffer, nil, 0)
  if yError != kvImageNoError {
      print("Can't scale a buffer")
      return
  }

  // create vImage_Buffer out of CVImageBuffer
  var uvInBuff: vImage_Buffer = vImage_Buffer()
  uvInBuff.width = UInt(CVPixelBufferGetWidth(imageBuffer))
  uvInBuff.height = UInt(CVPixelBufferGetHeight(imageBuffer))
  uvInBuff.rowBytes = CVPixelBufferGetBytesPerRow(imageBuffer)
  uvInBuff.data = CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 1)

  // perform scale of UV plane
  let uvError = vImageScale_CbCr8(&yInBuff, &uvScaleBuffer, nil, 0)
  if uvError != 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
  ]

  var planeBaseAddresses = [UnsafeMutableRawPointer?]()
  planeBaseAddresses.append(&yScaleBuffer.data)
  planeBaseAddresses.append(&uvScaleBuffer.data)

  var planeWidths = [Int]()
  planeWidths.append(Int(yScaleBuffer.width))
  planeWidths.append(Int(uvScaleBuffer.width))

  var planeHeights = [Int]()
  planeHeights.append(Int(yScaleBuffer.height))
  planeHeights.append(Int(uvScaleBuffer.height))

  var planeBytesPerRows = [Int]()
  planeWidths.append(yScaleBuffer.rowBytes)
  planeWidths.append(uvScaleBuffer.rowBytes)

  let status = CVPixelBufferCreateWithPlanarBytes(
    kCFAllocatorDefault,
    1280,
    720,
    kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange,
    nil,
    0,
    2,
    &planeBaseAddresses,
    &planeWidths,
    &planeHeights,
    &planeBytesPerRows,
    nil,
    nil,
    attributes as CFDictionary?,
    &newBuffer
  )

  guard status == kCVReturnSuccess,
        let b = newBuffer else {
      print("Can't create new CVPixelBuffer")
      return
  }

  // ... Then output the buffer to the screen (this uses a framework which accepts a CVPixelBuffer which I know works)
}

这不会产生错误，但我的输出只是绿色。这里出了什么问题？

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