app.Map("/logo", configuration =>
            {
                configuration.Use(async (context, next) =>
                {
                    LogoClass logo = new LogoClass();
                    System.IO.MemoryStream image = logo.Read("1");

                    что то типо такого
                    context.Response.ContentType = "image/jpeg";
                    await  image.copyto(context.Response.Body);
                });
            });