ImageContent.cs

   public class ImageContent : HttpContent
    {
       
        private Image _image;
       
        public ImageContent(Image image, MediaTypeHeaderValue mediatype)
        {
            _image = image;
            Headers.ContentType = mediatype;
        }

        protected async override Task SerializeToStreamAsync(Stream stream, TransportContext context)
        {
            
            var format = GetFormat(Headers.ContentType);
            _image.Save(stream, format);
            _image.Dispose();  // Once sent or buffered, then throw away image
            _image = null;
        }

        protected override bool TryComputeLength(out long length)
        {
            // If you really don't want to load it into a buffer,
            // then you will need to chunk encoding it because you don't know it's length
            length = -1;
            return false;
        }

        private static ImageFormat GetFormat(MediaTypeHeaderValue mediatype)
        {
            ImageFormat format = null;
            switch (mediatype.MediaType)
            {
                case "image/jpeg":
                    format = ImageFormat.Jpeg;
                    break;
                case "image/png":
                    format = ImageFormat.Png;
                    break;
                case "image/gif":
                    format = ImageFormat.Gif;
                    break;
                case "image/tiff":
                    format = ImageFormat.Tiff;
                    break;

                default:
                    throw new ArgumentException("Unsuppported media type");
            }
            return format;
        }
    
    }