呼叫方法：

ConvertTextFileToImage(Server.MapPath("~/Log.txt"),Server.MapPath("~/Log.png"));

實現程式碼：

  void ConvertTextFileToImage(String textFile,String imageFile)
  {
    System.Drawing.Font drawFont = new System.Drawing.Font("宋體", 12);
    System.Drawing.Bitmap image = new System.Drawing.Bitmap(1, 1);
    System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
    String text = System.IO.File.ReadAllText(textFile, Encoding.GetEncoding("GB2312"));
    System.Drawing.SizeF sf = g.MeasureString(text, drawFont, 1024); //設定一個顯示的寬度 
    image = new System.Drawing.Bitmap(image, new System.Drawing.Size(Convert.ToInt32(sf.Width), Convert.ToInt32(sf.Height)));
    g = System.Drawing.Graphics.FromImage(image);
    g.Clear(System.Drawing.Color.White);
    g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAliasGridFit;
    g.DrawString(text, drawFont, System.Drawing.Brushes.Black, new System.Drawing.RectangleF(new System.Drawing.PointF(0, 0), sf));
    image.Save(imageFile, System.Drawing.Imaging.ImageFormat.Png);
    g.Dispose();
    image.Dispose();
  }