When you can't set `-all_load` to Other Linker Flags

iosConversions.swift

// https://github.com/opencv/opencv/blob/master/modules/imgcodecs/src/ios_conversions.mm
// https://github.com/opencv/opencv/blob/master/modules/imgcodecs/src/apple_conversions.mm
func MatToCGImage(image:Mat) -> CGImage? {
  let data = Data(bytes: image.dataPointer(), count: image.step1() * Int(image.rows()))
  let colorSpace = image.elemSize() == 1 ? CGColorSpaceCreateDeviceGray() : CGColorSpaceCreateDeviceRGB()

  let provider = CGDataProvider(data: data as CFData);
  let alpha = image.channels() == 4;
  let bitmapInfo: CGBitmapInfo = CGBitmapInfo(rawValue: (alpha ? CGImageAlphaInfo.last : CGImageAlphaInfo.none).rawValue | CGBitmapInfo.byteOrderDefault.rawValue)

  let cgImage = CGImage(width: Int(image.cols()),
                        height: Int(image.rows()),
                        bitsPerComponent: 8 * image.elemSize1(),
                        bitsPerPixel: 8 * image.elemSize(),
                        bytesPerRow: image.step1(),
                        space: colorSpace,
                        bitmapInfo: bitmapInfo,
                        provider: provider!,
                        decode: nil,
                        shouldInterpolate: false,
                        intent: CGColorRenderingIntent.defaultIntent
  )

  return cgImage
}

func MatToUIImage(image:Mat) -> UIImage {
  let cgImage = MatToCGImage(image: image)
  return UIImage(cgImage: cgImage!)
}


func CGImageToMat(image: CGImage, alphaExist: Bool = false) -> Mat {

  var m = Mat()
  var colorSpace = image.colorSpace!
  let cols = CGFloat(image.width), rows = CGFloat(image.height)
  let context: CGContext?
  var bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)

  if (colorSpace.model == CGColorSpaceModel.monochrome)
  {
    m.create(rows: Int32(rows), cols: Int32(cols), type: CvType.CV_8UC1) // 8 bits per component, 1 channel
    bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue)
    if (alphaExist){
//        m = Scalar(0)
    }
  }
  else {
    if (colorSpace.model == CGColorSpaceModel.indexed)
    {
      // CGBitmapContextCreate() does not support indexed color spaces.
      colorSpace = CGColorSpaceCreateDeviceRGB();
    }
    m.create(rows: Int32(rows), cols: Int32(cols), type: CvType.CV_8UC4) // 8 bits per component, 4 channels
    if (!alphaExist){
      bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.noneSkipLast.rawValue | CGBitmapInfo.byteOrderDefault.rawValue )
    } else {
//        m = Scalar(0)
    }
  }

  context = CGContext(data: m.dataPointer(), width: Int(m.cols()), height: Int(m.rows()),
                      bitsPerComponent: 8,
                      bytesPerRow: m.step1(), space: colorSpace,
                      bitmapInfo: bitmapInfo.rawValue)
  context?.draw(image, in: CGRect(x: 0, y: 0, width: cols, height: rows))

  return m
}

func UIImageToMat(image: UIImage, alphaExist: Bool = false) -> Mat {
  return CGImageToMat(image: image.cgImage!, alphaExist: alphaExist)
}