问题：.NET Core使用System.Drawing.Common时找不到libgdiplus的问题
Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware[1]
An unhandled exception has occurred while executing the request.
System.TypeInitializationException: The type initializer for 'Gdip' threw an exception.
---> System.DllNotFoundException: Unable to load shared library 'libgdiplus' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: liblibgdiplus: cannot open shared object file: No such file or directory
at System.Drawing.SafeNativeMethods.Gdip.GdiplusStartup(IntPtr& token, StartupInput& input, StartupOutput& output)
at System.Drawing.SafeNativeMethods.Gdip..cctor()
--- End of inner exception stack trace ---
at System.Drawing.SafeNativeMethods.Gdip.GdipCreateBitmapFromScan0(Int32 width, Int32 height, Int32 stride, Int32 format, HandleRef scan0, IntPtr& bitmap)
at System.Drawing.Bitmap..ctor(Int32 width, Int32 height, PixelFormat format)
at CS.FTX.Web.Common.Extions.GetSecurityCode(String& code) in E:SourceDotNetCoreCS.FTXCS.FTX.WebCommonExtions.cs:line 56
at CS.FTX.Web.Controllers.AccountController.SecurityCode() in E:SourceDotNetCoreCS.FTXCS.FTX.WebControllersAccountController.cs:line 201
at lambda_method(Closure , Object , Object[] )
at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.SyncActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeActionMethodAsync()
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeNextActionFilterAsync()
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.
at Microsoft.AspNetCore.Routing.EndpointMiddleware.
at Microsoft.AspNetCore.Builder.Extensions.MapMiddleware.Invoke(HttpContext context)
at CS.FTX.Web.Common.RequiredAdminMiddleware.InvokeAsync(HttpContext context, IHttpContextAccessor httpContextAccessor) in E:SourceDotNetCoreCS.FTXCS.FTX.WebCommonRequiredAdminMiddleware.cs:line 54
at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
at IdentityServer4.Hosting.IdentityServerMiddleware.Invoke(HttpContext context, IEndpointRouter router, IUserSession session, IEventService events)
at IdentityServer4.Hosting.MutualTlsTokenEndpointMiddleware.Invoke(HttpContext context, IAuthenticationSchemeProvider schemes)
at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
at IdentityServer4.Hosting.BaseUrlMiddleware.Invoke(HttpContext context)
at Marvin.Cache.Headers.HttpCacheHeadersMiddleware.Invoke(HttpContext httpContext, IValidatorValueInvalidator validatorValueInvalidator)
at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware.
解决：
https://q.cnblogs.com/q/109061/
除了安装 libgdiplus 还要安装 libc6-dev
apt-get update
apt-get install -y --no-install-recommends libgdiplus libc6-dev ‘
分析：
为什么会找不到 libdl (libdl.so.2) 呢？
是因为 System.Drawing.Common 是在 /usr/lib/x86_64-linux-gnu/ 这个路径中找的，而容器中 libdl.so.2 存在于 /lib/x86_64-linux-gnu/ 目录中，
安装 libc6-dev 之后 /lib/x86_64-linux-gnu/ 中就有了 libdl.so.2 ，问题就解决了。
现在不需要 ln -s libgdiplus.so gdiplus.dll ，System.Drawing.Common 已经改了代码，直接加载 libgdiplus.so
声明：本问为坑的记录，参考资料如下
https://q.cnblogs.com/q/109061/
