public class SomeClass
{

public static string GetImageLargeThumbnail(string ImagePath)
        {
            string _fullFilePath = System.Web.HttpContext.Current.Server.MapPath(umbraco.GlobalSettings.Path + "/.." + ImagePath);
            string ext = System.IO.Path.GetExtension(_fullFilePath);
            string fileNameThumb = _fullFilePath.Replace(ext, "_thumblarge.jpg");

            if (!File.Exists(fileNameThumb))
            {

                using (System.Drawing.Image image = System.Drawing.Image.FromFile(_fullFilePath))
                {
                    CreateThumbnail(image, 201, 112, fileNameThumb);
                }
                System.Web.HttpContext.Current.Trace.Write("Created a thumbnail sucessfully");
            }

            return ImagePath.Replace(System.IO.Path.GetExtension(ImagePath), "_thumblarge.jpg");
        }

        private static void CreateThumbnail(Image image, int descWidth, int descHeight, string thumbFileName)
        {
                    using (Bitmap thumbnail = new Bitmap(descWidth, descHeight))
                    {
                        thumbnail.SetResolution(image.HorizontalResolution, image.VerticalResolution);

                        Graphics g = Graphics.FromImage(thumbnail);
                        g.InterpolationMode = InterpolationMode.HighQualityBicubic;

                        g.DrawImage(image,
                            new Rectangle(0, 0, descWidth, descHeight),
                            new Rectangle(0, 0, image.Width, image.Height),
                            GraphicsUnit.Pixel);

                        g.Dispose();

                        thumbnail.Save(thumbFileName, ImageFormat.Jpeg);
                    }
        }
}