12306动态验证码启发之ASP.NET实现动态GIF验证码(附源码)

12306网站推出“彩色动态验证码机制”，新版验证码不但经常出现字符叠压，还不停抖动，不少人大呼“看不清”，称“那个验证码，是毕加索的抽象画么!”铁总客服则表示:为了能正常购票只能这样。而多家抢票软件接近“报废”，引发不少网友不满的吐槽称“太抽象太艺术了”。
以前做项目有时候也会用到验证码，但基本都是静态的，这次也想凑凑12306的热闹。闲言少续，切入正题，先上代码。

实现方法：

 public void showcode()
    {
      //对象实例化
      validate gifvalidate = new validate();

      #region 对验证码进行设置(不进行设置时,将以默认值生成)
      //验证码位数，不小于4位
      gifvalidate.validatecodecount = 4;
      //验证码字体型号(默认13)
      gifvalidate.validatecodesize = 13;
      //验证码图片高度,高度越大,字符的上下偏移量就越明显
      gifvalidate.imageheight = 23;
      //验证码字符及线条颜色(需要参考颜色类)
      gifvalidate.drawcolor = system.drawing.color.blueviolet;
      //验证码字体(需要填写服务器安装的字体)
      gifvalidate.validatecodefont = "arial";
      //验证码字符是否消除锯齿
      gifvalidate.fonttextrenderinghint = false;
      //定义验证码中所有的字符(","分离),似乎暂时不支持中文
      gifvalidate.allchar = "1,2,3,4,5,6,7,8,9,0,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z";
      #endregion

      //输出图像(session名称)
      gifvalidate.outputvalidate("getcode");
    }

调用主要方法：

public class validate
  {
    public string allchar = "1,2,3,4,5,6,7,8,9,0,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z";
    public color drawcolor = color.blueviolet;
    public bool fonttextrenderinghint = false;
    public int imageheight = 0x17;
    private byte truevalidatecodecount = 4;
    protected string validatecode = "";
    public string validatecodefont = "arial";
    public float validatecodesize = 13f;

    private void createimagebmp(out bitmap imageframe)
    {
      char[] charray = this.validatecode.tochararray(0, this.validatecodecount);
      int width = (int) (((this.truevalidatecodecount * this.validatecodesize) * 1.3) + 4.0);
      imageframe = new bitmap(width, this.imageheight);
      graphics graphics = graphics.fromimage(imageframe);
      graphics.clear(color.white);
      font font = new font(this.validatecodefont, this.validatecodesize, fontstyle.bold);
      brush brush = new solidbrush(this.drawcolor);
      int maxvalue = (int) math.max((float) ((this.imageheight - this.validatecodesize) - 3f), (float) 2f);
      random random = new random();
      for (int i = 0; i < this.truevalidatecodecount; i++)
      {
        int[] numarray = new int[] { (((int) (i * this.validatecodesize)) + random.next(1)) + 3, random.next(maxvalue) };
        point point = new point(numarray[0], numarray[1]);
        if (this.fonttextrenderinghint)
        {
          graphics.textrenderinghint = textrenderinghint.singlebitperpixel;
        }
        else
        {
          graphics.textrenderinghint = textrenderinghint.antialias;
        }
        graphics.drawstring(charray[i].tostring(), font, brush, (pointf) point);
      }
      graphics.dispose();
    }

    private void createimagegif()
    {
      animatedgifencoder encoder = new animatedgifencoder();
      memorystream stream = new memorystream();
      encoder.start();
      encoder.setdelay(5);
      encoder.setrepeat(0);
      for (int i = 0; i < 10; i++)
      {
        bitmap bitmap;
        this.createimagebmp(out bitmap);
        this.disposeimagebmp(ref bitmap);
        bitmap.save(stream, imageformat.png);
        encoder.addframe(image.fromstream(stream));
        stream = new memorystream();
      }
      encoder.output(ref stream);
      httpcontext.current.response.clearcontent();
      httpcontext.current.response.contenttype = "image/gif";
      httpcontext.current.response.binarywrite(stream.toarray());
      stream.close();
      stream.dispose();
    }

    private void createvalidate()
    {
      this.validatecode = "";
      string[] strarray = this.allchar.split(new char[] { ',' });
      int index = -1;
      random random = new random();
      for (int i = 0; i < this.validatecodecount; i++)
      {
        if (index != -1)
        {
          random = new random((i * index) * ((int) datetime.now.ticks));
        }
        int num3 = random.next(0x23);
        if (index == num3)
        {
          this.createvalidate();
        }
        index = num3;
        this.validatecode = this.validatecode + strarray[index];
      }
      if (this.validatecode.length > this.truevalidatecodecount)
      {
        this.validatecode = this.validatecode.remove(this.truevalidatecodecount);
      }
    }

    private void disposeimagebmp(ref bitmap imageframe)
    {
      graphics graphics = graphics.fromimage(imageframe);
      pen pen = new pen(this.drawcolor, 1f);
      random random = new random();
      point[] pointarray = new point[2];
      for (int i = 0; i < 15; i++)
      {
        pointarray[0] = new point(random.next(imageframe.width), random.next(imageframe.height));
        pointarray[1] = new point(random.next(imageframe.width), random.next(imageframe.height));
        graphics.drawline(pen, pointarray[0], pointarray[1]);
      }
      graphics.dispose();
    }

    public void outputvalidate(string validatecodesession)
    {
      this.createvalidate();
      this.createimagegif();
      httpcontext.current.session[validatecodesession] = this.validatecode;
    }

    public byte validatecodecount
    {
      get
      {
        return this.truevalidatecodecount;
      }
      set
      {
        if (value > 4)
        {
          this.truevalidatecodecount = value;
        }
      }
    }
  }

验证码效果：       -----下载源码-----

以上就是实现asp.net的全部过程，还附有源码，希望可以帮到大家更好地了解asp.net验证码的生成方法。