c# 画布验证码

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

namespace WindowsFormsApplication3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void lblColor1_Click(object sender, EventArgs e)
        {
            Label lbl = sender as Label;
            ColorDialog cd = new ColorDialog();
            DialogResult dr = cd.ShowDialog();
            if (dr == System.Windows.Forms.DialogResult.OK)
            {
                lbl.BackColor = cd.Color;
            }
        }

        private void btnGenerate_Click(object sender, EventArgs e)
        {
            Random ran = new Random();
            string code = "";
            for (int i = 0; i < 4; i++)
            {
                char c = (char)ran.Next(65, 91);
                code += c;
            }
            int lineNum = 0;
            Bitmap bmp = null;
            if (!(int.TryParse(txtLineNum.Text, out lineNum) && ckLine.Checked))
            {
                VerifyCode vc = new VerifyCode();
                bmp = vc.Draw();
            }
            else
            {
                VerifyCode vc = new VerifyCode(ckLine.Checked, lblColor1.BackColor, lblColor2.BackColor, int.Parse(txtLineNum.Text), code);
                bmp = vc.Draw();
            }
            picImg.Image = bmp;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WindowsFormsApplication3
{
    public class VerifyCode
    {
        private bool _line = false;

        public bool Line
        {
            get { return _line; }
            set { _line = value; }
        }

        private Color _color1 = Color.Blue;

        public Color Color1
        {
            get { return _color1; }
            set { _color1 = value; }
        }
        private Color _color2 = Color.DarkRed;

        public Color Color2
        {
            get { return _color2; }
            set { _color2 = value; }
        }
        private int _lineNum = 20;

        public int LineNum
        {
            get { return _lineNum; }
            set { _lineNum = value; }
        }

        private string _code = "ABCD";

        public string Code
        {
            get { return _code; }
            set { _code = value; }
        }

        public VerifyCode()
        {
        }

        public VerifyCode(bool ckline, Color color1, Color color2, int lineNum, string code)
        {
            this.Line = ckline;
            this.Color1 = color1;
            this.Color2 = color2;
            this.LineNum = lineNum;
            this.Code = code;
        }

        public Bitmap Draw()
        {
            if (this.Line)
            {
                return DrawImg(this.Line);
            }
            else
            {
                return DrawImg();
            }

        }

        private Bitmap DrawImg()
        {
            Bitmap bmp = new Bitmap((int)Math.Ceiling(this.Code.Length * 12.5) + 2, 22);
            Graphics grap = Graphics.FromImage(bmp);
            grap.Clear(Color.White);

            Font font = new Font("Arial", 12, FontStyle.Regular);
            Rectangle r = new Rectangle(0, 0, bmp.Width, bmp.Height);
            LinearGradientBrush lgb = new LinearGradientBrush(r, this.Color1, this.Color2, 1.2f, true);
            grap.DrawString(this.Code, font, lgb, 0, 2);
            grap.Dispose();
            return bmp;
        }

        private Bitmap DrawImg(bool ckline)
        {
            Bitmap bmp = new Bitmap((int)Math.Ceiling(this.Code.Length * 12.5) + 2, 22);
            Graphics grap = Graphics.FromImage(bmp);
            grap.Clear(Color.White);

            //一半的干扰线
            Random random = new Random(); 
            for (int i = 0; i < this.LineNum/2; i++)
            {
                int x1 = random.Next(bmp.Width);
                int x2 = random.Next(bmp.Width);
                int y1 = random.Next(bmp.Height);
                int y2 = random.Next(bmp.Height);

                int int_Red = random.Next(256);
                int int_Green = random.Next(256);
                int int_Blue = (int_Red + int_Green > 400) ? 0 : 400 - int_Red - int_Green;
                int_Blue = (int_Blue > 255) ? 255 : int_Blue;
                grap.DrawLine(new Pen(Color.FromArgb(int_Red, int_Green, int_Blue)), x1, y1, x2, y2); 
            }

            Font font = new Font("Arial", 12, FontStyle.Regular);
            Rectangle r = new Rectangle(0, 0, bmp.Width, bmp.Height);
            LinearGradientBrush lgb = new LinearGradientBrush(r, this.Color1, this.Color2, 1.2f, true);
            grap.DrawString(this.Code, font, lgb, 0, 2);
            grap.Dispose();
            //一半的干扰点
            for (int i = 0; i < this.LineNum / 2; i++)
            {
                int x1 = random.Next(bmp.Width);
                int x2 = random.Next(bmp.Height);

                int int_Red = random.Next(256);
                int int_Green = random.Next(256);
                int int_Blue = (int_Red + int_Green > 400) ? 0 : 400 - int_Red - int_Green;
                int_Blue = (int_Blue > 255) ? 255 : int_Blue;

                bmp.SetPixel(x1, x2, Color.FromArgb(int_Red, int_Green, int_Blue));
            }

            
            return bmp;
        }
    }
}

效果