Yuebon.NetCore/Yuebon.Commons/VerificationCode/Captcha.cs

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

namespace Yuebon.Commons.VerificationCode
{
    /// <summary>
    /// 验证码实现
    /// </summary>
    public class Captcha 
    {
        private const string Letters = "1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";
        /// <summary>
        /// 生成验证码图片
        /// </summary>
        /// <param name="captchaCode">验证码</param>
        /// <param name="width">图形宽度，默认为验证码长度x25</param>
        /// <param name="height">图形高度，默认30px</param>
        /// <returns></returns>
        public async Task<CaptchaResult> GenerateCaptchaImageAsync(string captchaCode, int width = 0, int height = 30)
        {

            //验证码颜色集合
            Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };

            //验证码字体集合
            string[] fonts = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };

            //定义图像的大小，生成图像的实例
            var image = new Bitmap(width == 0 ? captchaCode.Length * 25 : width, height);

            var g = Graphics.FromImage(image);

            //背景设为白色
            g.Clear(Color.White);

            var random = new Random();
            // 画图片的背景噪音线
            for (var i = 0; i < 100; i++)
            {
                var x = random.Next(image.Width);
                var y = random.Next(image.Height);
                g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
            }

            //验证码绘制在g中
            for (var i = 0; i < captchaCode.Length; i++)
            {
                //随机颜色索引值
                var cindex = random.Next(c.Length);

                //随机字体索引值
                var findex = random.Next(fonts.Length);

                //字体
                var f = new Font(fonts[findex], 15, FontStyle.Bold);

                //颜色  
                Brush b = new SolidBrush(c[cindex]);