.netCore 图形验证码，非System.Drawing.Common_sixlabors.imagesharp 验证码

netcore需要跨平台，说白点就是放在windows服务器要能用，放在linux服务器上也能用，甚至macos上。

很多时候需要使用到图形验证码，这就有问题了。

旧方案

1.引入包

    <PackageReference Include="System.Drawing.Common" Version="5.0.3" />

2.添加引用

using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;

3.在linux上安装libgdiplus

问题在于这个libgdiplus东西非常大，这个东西是moon兼容而来的，而且！！！.net6.0开始不支持这个东西了。

新方案

1.安装包

    <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="1.0.0-beta15" />

要勾选预览版，不然找不到这个包

2.添加引用

using SixLabors.Fonts;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Drawing.Processing;
using SixLabors.ImageSharp.Formats.Jpeg;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing;

3.生成一个验证码图片

        public byte[] CreateByteByImgVerifyCode(string verifyCode, int width, int height)
        {
 
            using Image image = new Image<Rgba32>(width, height);
            //漆底色白色
            image.Mutate(x => x.DrawLines(Pens.DashDot(Color.White, width), new PointF[] { new PointF() { X = 0, Y = 0 }, new PointF() { X = width, Y = height } }));
 
            FontCollection collection = new();
            FontFamily family = collection.Add("font/font.ttf");
            Font font = family.CreateFont(20, FontStyle.Bold);
 
            PointF startPointF = new PointF(5, 5);
            Random random = new Random(); //随机数产生器
 
            Color[] colors = new Color[] { Color.Red, Color.Blue, Color.Green, Color.Purple, Color.Peru, Color.LightSeaGreen, Color.Lime, Color.Magenta, Color.Maroon, Color.MediumBlue, Color.MidnightBlue, Color.Navy };
            //绘制大小
            for (int i = 0; i < verifyCode.Length; i++)
            {
                image.Mutate(x => x.DrawText(verifyCode[i].ToString(), font, colors[random.Next(colors.Length)], startPointF));
                //Console.WriteLine($"draw code:{verifyCode[i]} point:{startPointF.X}-{startPointF.Y}");
                startPointF.X += (int)(width - 10) / verifyCode.Length;
                startPointF.Y = random.Next(5, 10);
            }
 
            IPen pen = Pens.DashDot(Color.Silver, 1);
 
            //绘制干扰线
            for (var k = 0; k < 40; k++)
            {
                PointF[] points = new PointF[2];
                points[0] = new PointF(random.Next(width), random.Next(height));
                points[1] = new PointF(random.Next(width), random.Next(height));
                image.Mutate(x => x.DrawLines(pen, points));
            }
 
 
            using MemoryStream stream = new MemoryStream();
            image.Save(stream, JpegFormat.Instance);
            //输出图片流  
            return stream.ToArray();
 
        }

4.在controller中调用它

        [HttpGet]
        public FileContentResult Code(string guid)
        {
            try
            {
                if (String.IsNullOrEmpty(guid))
                {
                    throw new Exception("验证码代码错误，guid不能为空!");
                }
 
                //进行特殊符号的替换工作
                if (!new System.Text.RegularExpressions.Regex("[0-9,a-z,A-Z]{16}").Match(guid).Success)
                {
                    throw new Exception("guid的位数不足，应为16位随机数，不能包含特殊符号，需要为字母和数字的组合");
                }
 
                if (_cache.KeyExits(string.Format(PublicString.CacheImageHead, guid))) { throw new Exception("guid不能重复使用！"); }
 
                //判断guid是否存在
 
                string code = _imgHelper.CreateVerifyCode(ImageHelper.VerifyCodeType.NumberVerifyCode);
 
                _cache.SetString(string.Format(PublicString.CacheImageHead, guid), code, 300);
 
                byte[] codeImage = _imgHelper.CreateByteByImgVerifyCode(code, 80, 36);
 
                return File(codeImage, @"image/jpeg");
            }
            catch (Exception exl)
            {
                _logger.LogException(exl);
                throw new Exception(exl.Message);
            }
        }

5.随机数计算，缓存帮助类自己实现。

6.新方案不需要安装libgdiplus

7.旧方案占用内存很大，新方案内存消耗很划算

附上一个Dockerfile的文件内容

FROM mcr.microsoft.com/dotnet/aspnet:6.0-alpine AS base
# 安装tzdata
RUN sed -i 's/dl-cdn.alpinelinux.org/mirrors.aliyun.com/g' /etc/apk/repositories
RUN apk add --no-cache tzdata
#RUN apk add libgdiplus --update-cache --repository http://dl-3.alpinelinux.org/alpine/edge/testing/ --allow-untrusted
#RUN apk add terminus-font
# 设置时区
ENV TZ="Asia/Shanghai"
ENV LANG C.UTF-8
 
FROM base AS final
WORKDIR /app
EXPOSE 80
COPY . .
 
ENTRYPOINT ["dotnet", "xxx.HttpApi.Host.dll"]