上传带水印的图片、图片验证码

一、图片加水印

前台代码：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default1.aspx.cs" Inherits="Default1" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:FileUpload ID="FileUpload1" runat="server" /><asp:Button ID="Button1" runat="server" Text="上传" /><br />
        <asp:Image ID="Image1" runat="server" />
    </div>
    </form>
</body>
</html>

后台代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;

public partial class Default1 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Button1.Click += Button1_Click;
    }

    void Button1_Click(object sender, EventArgs e)
    {
        //1、先把图片获取出来
        //咱们要画画的画布
        System.Drawing.Image img = System.Drawing.Image.FromStream(FileUpload1.FileContent);

        //2、往上面画上水印
        Graphics g = Graphics.FromImage(img);//这个是绘制方法，等号右边是往那张图片上绘制
        string s = "http://www.itnba.com"; //绘制的字符串
        Font f = new Font("微软雅黑",18);//绘制使用的字体
        SolidBrush b = new SolidBrush(Color.Red);//绘制使用的刷子，设置颜色

        g.DrawString(s, f, b, 0, 0); //绘制完毕

        //3、保存到服务器指定路径，并且在Image控件中显示
        string path = Server.MapPath("Uploads/" + FileUpload1.FileName);

        img.Save(path);//将绘制完的图片保存，注意：千万不要把选择的图片保存

        Image1.ImageUrl = "Uploads/" + FileUpload1.FileName;

    }
}

二、图片验证码

1、首先引用命名空间：system.Drawing;

2、将aspx页面当做图片路径，在load事件中进行绘制并保存在内存流中

前台代码：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        请输入验证码：<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox><asp:Image ID="Image1" runat="server" ImageUrl="~/YZM.aspx" /><br />
        <asp:Button ID="Button1" runat="server" Text="验证" /><asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
    </div>
    </form>
</body>
</html>
<script type="text/javascript">
    var aaa = 0;
    document.getElementById('Image1').onclick = function () {
        this.setAttribute("src", "yzm.aspx?id="+aaa);
        aaa++;

    };

</script>

后台代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Button1.Click += Button1_Click;
    }

    void Button1_Click(object sender, EventArgs e)
    {
        if (TextBox1.Text == Session["YZM"].ToString())
        {
            Label1.Text = "正确！";
        }
        else
        {
            Label1.Text = "错误！";
        }
    }
}

生成图片验证码的后台代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;

public partial class YZM : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //1、准备画布
        Bitmap img = new Bitmap(60, 30);

        //2、往画布上绘制验证码

        string all = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
        string aaa = "";
        Random r = new Random();
        for (int i = 0; i < 4; i++)
        {
            aaa += all.Substring(r.Next(all.Length), 1);
        }

        Session["YZM"] = aaa;
        Graphics g = Graphics.FromImage(img);
        Font f = new Font("微软雅黑",16);
        SolidBrush b  = new SolidBrush(Color.Green);

        g.DrawString(aaa, f, b, 0, 0);

        img.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Png);
    }
}