public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            String foo = File.ReadAllText("c:\\jim.txt").Trim().Replace("\n", "").Replace("\r", "");

            Debug.Print(foo.Length.ToString());

            Byte[] bar = StringToByteArray(foo);

            Debug.Print(bar.Length.ToString());

            File.WriteAllBytes("bob.jpg", bar);

            pictureBox1.Image = new Bitmap("bob.jpg");
        }

        public static byte[] StringToByteArray(string hex)
        {
            return Enumerable.Range(0, hex.Length).
                   Where(x => 0 == x % 2).
                   Select(x => Convert.ToByte(hex.Substring(x, 2), 16)).
                   ToArray();
        }
    }