SkiaSharp跨平台绘图研究3Asp.Net Core网站

SkiaSharp跨平台绘图研究3-Asp.Net Core网站

新建Asp.Net Core网站项目

新建Asp.Net Core Web（视图-模型-控制器）项目WebMvcDemo。

NuGet安装最新预览版SkiaSharp 2.88.0-preview.155。

在主页上放一个SkiaSharp画布，点击一下可以刷新，这个方案很常见，例如图片验证码。

@{
    ViewData["Title"] = "Home Page";
}

<div class="text-center">
    <h1 class="display-4">Welcome</h1>
    <p>Learn about <a href="https://docs.microsoft.com/aspnet/core">building Web apps with ASP.NET Core</a>.</p>
    <h4>SkiaSharp绘图</h4>
    <button class="btn btn-primary m-1" onclick="OnClickImg()" type="button">更新绘图</button>
    <br />
    <img src="/Home/GetImg" alt="pic" class="img-thumbnail" width="600" height="300" id="imgCaptcha" onclick="OnClickImg()" title="点击图片更新" />
</div>

@section Scripts {

<script type="text/javascript">

    function OnClickImg() {
        //确保URL每秒有变化，否则浏览器不去访问服务端
        var date = new Date();
        var src = "/Home/GetImg?id=" + date.getTime();
        document.getElementById("imgCaptcha").src = src;
    }
</script>
}

后台控制台Action每次新建一个图片文件返回给前端网页，绘图代码跟之前的WPF项目基本类似。字体文件也跟WPF项目那样复制都输出目录。

        /// <summary>
        /// 创建Skia图片
        /// </summary>
        /// <param name="id">前端html设置img的src的id参数变化，可以更新图片</param>
        /// <returns></returns>
        public IActionResult GetImg(string id)
        {
            _logger.LogInformation($"{DateTime.Now}, 开始创建图片");

            //创建画布的容器
            var info = new SKImageInfo(600, 300);
            using var surface = SKSurface.Create(info);
            var canvas = surface.Canvas;

            canvas.Clear(SKColors.SkyBlue);

            using var paint = new SKPaint
            {
                Color = SKColors.Black,
                IsAntialias = true,
                Typeface = SkiaChinaFont.ChinaFont,
                TextSize = 24
            };

            string msg = $"{DateTimeOffset.Now:T}, 还有1万行Skia绘图代码...";
            canvas.DrawText(msg, 0, 30, paint);

            using var linePaint = new SKPaint()
            {
                Color = (DateTimeOffset.Now.Second % 4 <= 1) ? SKColors.Red : SKColors.Green,
                Style = SKPaintStyle.Stroke,//不填充
                StrokeWidth = 3,
            };
            canvas.DrawRect(10, 50, info.Width - 20, info.Height - 60, linePaint);

            msg += $", linePaint.Color={linePaint.Color}, skContainer.CanvasSize={info.Size}";
            Debug.WriteLine(msg);

            //把画布容器转换为图片文件
            using var image = surface.Snapshot();
            using var data = image.Encode(SKEncodedImageFormat.Png, 100);

            return File(data.ToArray(), "image/png");

        }

然后把网站跑起来，可以在浏览器中看到图片，点击图片可以刷新内容。

 

发布到Linux云服务器测试

把网站发布到本机硬盘目录，打开控制台，运行网站，打开浏览器访问网站，测试没问题，再把发布目录拖到腾讯云CentOS操作系统测试。

在云服务器测试发现，必须绑定正确的域名证书，不然侦听https失败，但是控制台并没有提示https绑定错误信息，并且http侦听端口也是80。绑定域名证书后才能正确侦听指定端口。

skiawebmvc    | {"EventId":14,"LogLevel":"Information","Category":"Microsoft.Hosting.Lifetime","Message":"Now listening on: http://0.0.0.0:7900","State":{"Message":"Now listening on: http://0.0.0.0:7900","address":"http://0.0.0.0:7900","{OriginalFormat}":"Now listening on: {address}"}}

skiawebmvc    | {"EventId":14,"LogLevel":"Information","Category":"Microsoft.Hosting.Lifetime","Message":"Now listening on: https://0.0.0.0:7901","State":{"Message":"Now listening on: https://0.0.0.0:7901","address":"https://0.0.0.0:7901","{OriginalFormat}":"Now listening on: {address}"}}

打开网站主页，无法显示图片，云服务器控制台显示错误信息：

System.TypeInitializationException: The type initializer for \u0027SkiaSharp.SKImageInfo\u0027 threw an exception.  ---\u003E System.DllNotFoundException: Unable to load shared library \u0027libSkiaSharp\u0027 or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: liblibSkiaSharp: cannot open shared object file: No such file or directory

因为Skia在Linux平台上依赖一个库文件，所以要把这个库文件安装到容器里边，以前我用了一个比较麻烦的方法，去下载libSkiaSharp.so，设置文件属性为复制到输出目录，并修改dockerfile在构建容器时安装依赖库。

RUN echo "deb http://mirrors.aliyun.com/debian wheezy main contrib non-free \

deb-src http://mirrors.aliyun.com/debian wheezy main contrib non-free \

deb http://mirrors.aliyun.com/debian wheezy-updates main contrib non-free \

deb-src http://mirrors.aliyun.com/debian wheezy-updates main contrib non-free \

deb http://mirrors.aliyun.com/debian-security wheezy/updates main contrib non-free \

deb-src http://mirrors.aliyun.com/debian-security wheezy/updates main contrib non-free" > /etc/apt/sources.list

RUN apt-get update && apt-get install libfontconfig1 -y

后来了解到有一个NuGet包SkiaSharp.NativeAssets.Linux.NoDependencies，安装它就可以了，不用修改dockerfile，真是太神奇了。

    <PackageReference Include="SkiaSharp.NativeAssets.Linux.NoDependencies" Version="2.88.0-preview.155" />

可以参考这篇文章。

https://www.cnblogs.com/yycelsu/p/14048859.html

《Docker环境下使用SkiaSharp的2种方式 - 从零开始-DotNET技术 - 博客园》

因此dockerfile可以很简单了

FROM mcr.microsoft.com/dotnet/aspnet:6.0

WORKDIR /app
COPY . /app
#EXPOSE 5000
ENTRYPOINT ["dotnet", "WebMvcDemo.dll"]

Docker compose脚本文件也很简单

version: '3'

services:

  skiawebmvc:
    container_name: skiawebmvc
    image: skiawebmvcimage
    build:
      context: /home/skiawebmvc/skiawebmvcpub
      dockerfile: Dockerfile
    ports:
      - "7900:7900"
      - "7901:7901"
    environment:
      - ASPNETCORE_ENVIRONMENT=Production
      #- ASPNETCORE_ENVIRONMENT=Development
      - TZ=Asia/Shanghai
    volumes:
      - ./aspnetkeys:/root/.aspnet/DataProtection-Keys
      - ./myweb.pfx:/app/myweb.pfx
    restart: always

再次访问网站，图片出来了。

 

DEMO源代码参见：https://gitee.com/woodsun/skia-sharp-demo