CheckCode.aspx.cs

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using System;
using System.Web;
using System.Drawing.Imaging;
using System.Drawing;
using System.IO;

public partial class CheckCode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        ShowImg();
    }
    private void ShowImg()
    {
        Random ran = new Random();
        int intRandom = ran.Next(10001, 99999);
        //将随机数(验证字串)写入Session
        Session["checkcode1"] = intRandom;
        //字体名
        string strFontName = "Arial";
        //字体大小
        int intFontSize = 12;
        //图像宽
        int intWidth = 55;
        //图像长
        int intHeight = 20;
        //背景颜色
        Color bgColor = ColorTranslator.FromHtml("#" + Request.QueryString["colorb"]);
        //前景颜色
        Color foreColor = ColorTranslator.FromHtml("#" + Request.QueryString["colorf"]);
        //产生字体
        Font forFont = new Font(strFontName, intFontSize, FontStyle.Italic | FontStyle.Bold);
        //生成图片
        Bitmap newBitmap = new Bitmap(intWidth, intHeight, PixelFormat.Format32bppArgb);
        Graphics g = Graphics.FromImage(newBitmap);
        //定义一个四方形框与字片一样大小
        Rectangle newRect = new Rectangle(0, 0, intWidth, intHeight);
        //涂上背景色
        g.FillRectangle(new SolidBrush(bgColor), newRect);

        //写字
        //g.DrawString(intRandom.ToString(), forFont, new SolidBrush(foreColor), 2, 2);//原本（以下2句是修改后的）
        System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, newBitmap.Width, newBitmap.Height), Color.Yellow, Color.Violet, 1.2f, true);
        g.DrawString(intRandom.ToString(), forFont, brush, 2, 2);

        MemoryStream mStream = new MemoryStream();
        //存入MemoryStream
        newBitmap.Save(mStream, ImageFormat.Gif);
        g.Dispose();
        newBitmap.Dispose();
        //发送
        Response.ClearContent();
        Response.ContentType = "image/GIF";
        Response.BinaryWrite(mStream.ToArray());
        Response.End();
    }
}