struct raw_image
{
   void* data;
   int size;
};

ALIGNMENT_API void submit( raw_image& img )
{
    cv::Mat mat = cv::imdecode( cv::_InputArray(
        static_cast<uchar*>( img.data ), img.size ), cv::IMREAD_COLOR );
    cv::imshow( "image", mat );
    cv::waitKey( );
    cv::destroyWindow( "image" );
}

[StructLayout( LayoutKind.Sequential )]
internal unsafe struct RawImage
{
    internal void* ImageData;
    internal int Length;
}

[DllImport( "alignment-vc141-mtd-x64.dll", CallingConvention =
 CallingConvention.Cdecl )]
    static extern void submit( RawImage img );

using( var bitmap = new Bitmap( "AlignmentCenter.jpg" ) )
using( var stream = new MemoryStream( ) )
{
    bitmap.Save( stream, ImageFormat.Jpeg );
    var source = stream.ToArray( );
    fixed( void* ptr = source )
    {
        var raw = new RawImage
        {
            ImageData = ptr,
            Length = source.Length
        };
        submit( raw );
     }
  }