have look at the following code .This might help u:
string file=oHttpPostedFile.FileName;
Bitmap bitmap = new Bitmap(file);
Graphics graphics = null;
graphics = Graphics.FromImage(bitmap);
graphics.SmoothingMode = SmoothingMode.AntiAlias; graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
Bitmap bit = new Bitmap(AppDomain.CurrentDomain.BaseDirectory + "images/xyz");
int imgHeight = bitmap.Height;
int imgWidth = bitmap.Width;
graphics.DrawImage(bit, new Rectangle(imgWidth - 300, imgHeight - 160, 500, 77), 0, 0, 500, 77, GraphicsUnit.Pixel);
graphics.Dispose();
string file = AppDomain.CurrentDomain.BaseDirectory + "/Resources/NewImages/";
bitmap.Save(file + fileUpload1.FileName);