/// <summary>
/// 根据指定参数返回BitMap对象
/// 引用如下：
/// using System.Drawing;
/// 调用例子如下：
/// eg1、保存为图象文件为
/// Bitmap srBmp = srBitmap(srs);
/// srBmp.Save(Directory.GetCurrentDirectory() + "\\srs.gif", System.Drawing.Imaging.ImageFormat.Gif);
/// srBmp.Dispose();
/// eg2。网页中调用方式如下
/// Bitmap srBmp = srBitmap(srs);
/// System.IO.MemoryStream srMS = new System.IO.MemoryStream();
/// srBmp.Save(srMS,System.Drawing.Imaging.ImageFormat.Gif);
/// Response.ClearContent();
/// Response.ContentType = "image/gif";
/// Response.BinaryWrite(srMS.ToArray());
/// srBmp.Dispose();
/// </summary>
/// <param name="srs"></param>
/// <returns></returns>
public static Bitmap srBitmap(string srs)
{
