General.Core/Common/CaptchaHelper.cs

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

namespace General.Core.Common
{
    public class CaptchaHelper
    {
        #region 得到验证码
        /// <summary>
        /// Tuple第一个值是表达式，第二个值是表达式结果
        /// </summary>
        /// <returns></returns>
        public static Tuple<string, int> GetCaptchaCode()
        {
            int value = 0;
            char[] operators = { '+', '-', '*' };
            string randomCode = string.Empty;
            Random random = new Random();

            int first = random.Next() % 10;
            int second = random.Next() % 10;
            char operatorChar = operators[random.Next(0, operators.Length)];
            switch (operatorChar)
            {
                case '+': value = first + second; break;
                case '-':
                    // 第1个数要大于第二个数
                    if (first < second)
                    {
                        int temp = first;
                        first = second;
                        second = temp;
                    }
                    value = first - second;
                    break;
                case '*': value = first * second; break;
            }

            char code = (char)('0' + (char)first);
            randomCode += code;
            randomCode += operatorChar;
            code = (char)('0' + (char)second);
            randomCode += code;
            randomCode += "=?";
            return new Tuple<string, int>(randomCode, value);
        }
        #endregion

        #region 生成验证码图片
        /// <summary>
        /// 生成验证码图片
        /// </summary>
        /// <param name="randomCode"></param>
        /// <returns></returns>
        public static byte[] CreateCaptchaImage(string randomCode)
        {
            const int randAngle = 45; //随机转动角度
            int mapwidth = (int)(randomCode.Length * 16);