string str = "This is a\r\n test Message";
Bitmap img = new Bitmap(1, 1);
Graphics g = Graphics.FromImage(img);
Font f = new Font("Arial", 14);
SizeF size = g.MeasureString(str, f);
img = new Bitmap((int)Math.Ceiling(size.Width), (int)Math.Ceiling(size.Height));
g = Graphics.FromImage(img);
g.Clear(Color.White);
g.DrawString(str, f, Brushes.Black, 0, 0);
img.Save(@"c:\temp\Hello.jpg");