How to Get the Average Color of a UIImage Excluding the Transparent Parts

Question

How do I get the average color of the non-transparent parts of an image?

I get that you can get the average color of an image using the block of code below, but it also factors in the transparent parts to the calculation.

var averageColor: UIColor? {
    guard let inputImage = CIImage(image: self) else { return nil }
    let extentVector = CIVector (
      x: inputImage.extent.origin.x,
      y: inputImage.extent.origin.y,
      z: inputImage.extent.size.width,
      w: inputImage.extent.size.height)

    guard let filter = CIFilter (
      name: "CIAreaAverage",
      withInputParameters: [
        kCIInputImageKey: inputImage,
        kCIInputExtentKey: extentVector
    ]) else { return nil }
    guard let outputImage = filter.outputImage else { return nil }

    var bitmap = [UInt8](repeating: 0, count: 4)
    let context = CIContext(options: [kCIContextWorkingColorSpace: kCFNull])
    context.render (
      outputImage,
      toBitmap: &bitmap,
      rowBytes: 4,
      bounds: CGRect(x: 0, y: 0, width: 1, height: 1),
      format: kCIFormatRGBA8,
      colorSpace: nil
    )

    return UIColor (
      red: CGFloat(bitmap[0]) / 255,
      green: CGFloat(bitmap[1]) / 255,
      blue: CGFloat(bitmap[2]) / 255,
      alpha: CGFloat(bitmap[3]) / 255
    )
  }