C#验证码

public Form1()
{
InitializeComponent();
}

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

//创建画笔(颜色)
Pen npen = new Pen(Brushes.Red);

//创建两个点
Point n1 = new Point(20, 20);
Point n2 = new Point(255, 255);

g.DrawLine(npen, n1, n2);

}

private void Form1_Paint(object sender, PaintEventArgs e)
{
Graphics g = this.CreateGraphics();//创建GDI对像

//创建画笔(颜色)
Pen npen = new Pen(Brushes.Red);

//创建两个点
Point n1 = new Point(20, 20);
Point n2 = new Point(255, 255);

g.DrawLine(npen, n1, n2);

}

private void button2_Click(object sender, EventArgs e)
{
Graphics ng = this.CreateGraphics();

//创建画笔
Pen npen = new Pen(Brushes.Red);

Size sz=new System.Drawing.Size(100,100);
Rectangle res = new Rectangle(new Point(50, 50), sz);

ng.DrawRectangle(npen, res);
}

private void button3_Click(object sender, EventArgs e)
{
Graphics g = this.CreateGraphics();

Pen npen = new Pen(Brushes.Blue);

Size sz = new System.Drawing.Size(180, 180);

Rectangle rec = new Rectangle(new Point(150, 150), sz);

g.DrawPie(npen, rec, -50, -50);
}

private void pictureBox1_DoubleClick(object sender, EventArgs e)
{
Random rd = new Random();
string str = null;

for (int i = 0; i < 5; i++)
{
int n1=rd.Next(1, 10);
str += n1;
}

Bitmap bmp=new Bitmap(120,40);
//创建gdi
Graphics gd = Graphics.FromImage(bmp);

//画图
for (int i = 0; i < str.Length; i++)
{
Point pt = new Point(i * 20, 0);
string[] fonts={"微软雅黑","宋体","黑体","隶书","仿宋"};
Color[] colors={Color.Red,Color.Black,Color.Blue,Color.Orange,Color.Plum};
gd.DrawString(str[i].ToString(), new Font(fonts[rd.Next(0, 5)], 15, FontStyle.Bold), new SolidBrush(colors[rd.Next(0, 5)]), pt);
}
//给图片加线
for (int i = 0; i < 20; i++)
{
Point xpt1 = new Point(rd.Next(0, bmp.Width), rd.Next(0, bmp.Height));
Point xpt2 = new Point(rd.Next(0, bmp.Width), rd.Next(0, bmp.Height));
gd.DrawLine(new Pen(Brushes.Red), xpt1, xpt2);
}

//给图片加点
for (int i = 0; i < 50; i++)
{
Point p1 = new Point(rd.Next(0, bmp.Width), rd.Next(0, bmp.Height));
bmp.SetPixel(p1.X, p1.Y, Color.Black);
}
//将图片放到pictureBox中
pictureBox1.Image = bmp;
}