GDI+在绘制验证码中的使用

GDI+最简单的理解就是用来绘图的。其中包括点、直线、矩形、字符串等等。

先简单来个例子，说明如何在winform窗体中绘制一条直线，并且这条直线不随着窗体的移动而消失。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace GDIDemo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //一根笔 一张纸 两点 绘制直线的对象
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //创建一个GDI对象
            Graphics g = this.CreateGraphics();//new Graphics();

            //创建一支画笔对象
            Pen pen = new Pen(Brushes.Yellow);

            //创建两个点
            Point p1 = new Point(, );
            Point p2 = new Point(, );

            g.DrawLine(pen, p1, p2);
        }

        /// <summary>
        /// 重新绘制窗体的时候，直线也重新画一遍
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            //创建一个GDI对象
            Graphics g = this.CreateGraphics();//new Graphics();

            //创建一支画笔对象
            Pen pen = new Pen(Brushes.Yellow);

            //创建两个点
            Point p1 = new Point(, );
            Point p2 = new Point(, );

            g.DrawLine(pen, p1, p2);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Graphics g = this.CreateGraphics();
            Pen pen = new Pen(Brushes.Yellow);
            Size size=new System.Drawing.Size(,);
            Rectangle rec = new Rectangle(new Point(,),size);
            g.DrawRectangle(pen, rec);
        }
    }
}

GDI绘制直线

那么有了基本的了解就可以用类似的方法来绘制验证码了。主要包括绘制字符串、直线、点三部分，在BitMap位图上面绘制，然后将整个图片镶嵌到PictureBox中，单击该控件爱你，验证码发生变化。具体代码如下

 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Data;
 using System.Drawing;
 using System.Linq;
 using System.Text;
 using System.Windows.Forms;

 namespace 点击生成验证码
 {
     public partial class Form1 : Form
     {
         public Form1()
         {
             InitializeComponent();
         }

         /// <summary>
         /// 点击更换验证码
         /// </summary>
         /// <param name="sender"></param>
         /// <param name="e"></param>
         private void pictureBox1_Click(object sender, EventArgs e)
         {
             Random r = new Random();
             string str = null;
             for (int i = ; i < ; i++)
             {
                 int rNumber = r.Next(, ); //产生5个验证码随机数
                 str += rNumber.ToString();

             }

             Bitmap bmp = new Bitmap(, );
            //创建一个GDI对象
             Graphics g = Graphics.FromImage(bmp); //可以理解为将位图作为画布

             //绘制验证码上面的数字
             for (int i = ; i < ; i++)
             {
                 Point p=new Point(i*,); //此处的相对位置，不是相对窗体的，而是相对于pictureBox控件的
                 string[] font = {"微软雅黑","宋体","黑体","隶书","仿宋" };
                 Color[] colors = { Color.Yellow, Color.Blue, Color.Black, Color.Red, Color.Green };

                 g.DrawString(str[i].ToString(), new Font(font[r.Next(,)],,FontStyle.Bold),new SolidBrush(colors[r.Next(,)]), p); //此处注意字体对象包括字体、像素、加粗与否等等

             }

             //绘制验证码上面的线
             for (int i = ; i < ; i++)
             {
                 Point p1 = new Point(r.Next(, bmp.Width), r.Next(, bmp.Height));
                 Point p2 = new Point(r.Next(, bmp.Width), r.Next(, bmp.Height));
                 g.DrawLine(new Pen(Brushes.Green), p1, p2);
             }

             //将验证码上面加一些小点点
             for (int i = ; i < ; i++)
             {
                 Point p3 = new Point(r.Next(, bmp.Width), r.Next(, bmp.Height));
                 bmp.SetPixel(p3.X,p3.Y,Color.Yellow);
             }
             //将画好的位图赋值给Image属性,即将画好的图片镶嵌到pictureBox中
             pictureBox1.Image = bmp;
         }
     }
 }

绘制数字验证码

实现效果图：