public class MediaRequestOverride : MediaProvider
    {
        public override Media GetMedia(MediaUri mediaUri)
        {
            var mediaData = GetMediaData(mediaUri);
            var media = GetMedia(mediaData);

            return GetMediaFace(media);

        }
        public override Media GetMedia(MediaItem item)
        {
            var mediaData = GetMediaData(item);
            var media = GetMedia(mediaData);

            return GetMediaFace(media);
        }

        public Media GetMediaFace(Media media)
        {
            using (new SecurityDisabler())
            {
                var stream = media.GetStream();

                var resultingBitmap = DetectFact(Image.FromStream(stream.Stream));

                if (resultingBitmap == null)
                    return media;

                var memoryStream = new MemoryStream();
                resultingBitmap.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Jpeg);

                media.SetStream(memoryStream, "jpeg");
            }
            return media;
        }

        private Bitmap DetectFact(Image imageFromBitmap)
        {
            var imageBitmap = new Bitmap(imageFromBitmap);
            var image = new Image<Bgr, byte>(imageBitmap);
            var gray = image.Convert<Gray, Byte>();
            var face = new HaarCascade("haarcascade_frontalface_default.xml");

            var facesDetected = gray.DetectHaarCascade(face, 1.1, 4, HAAR_DETECTION_TYPE.DO_CANNY_PRUNING, new Size(20, 20));

            Graphics g= null;

            foreach (var f in facesDetected[0])
            {
                using (g = Graphics.FromImage(imageBitmap))
                {
                    g.DrawRectangle(new Pen(Color.Red, 5), f.rect);
                    g.Save();
                } 

                break;
            }

            if (g != null)
                return imageBitmap;

            return null;

        }
    }