OrBitMesinterface/OrBit.MesFileServer.Host/Middleware/ThumbnailMiddleware.cs

using Microsoft.Extensions.Options;
using OrBit.MesFileServiceNode.Host.Model;
using System.Drawing;
using System.Drawing.Imaging;

namespace OrBit.MesFileServiceNode.Host.Middleware
{
    public class ThumbnailMiddleware : IMiddleware
    {
        private NodeConfig _config;

        public ThumbnailMiddleware(IOptions<NodeConfig> config)
        {
            _config = config.Value;
        }

        public Task InvokeAsync(HttpContext context, RequestDelegate next)
        {
            if (context.Request.Query.ContainsKey("w") || context.Request.Query.ContainsKey("h"))
            {
                var ext = Path.GetExtension(context.Request.Path);
                //不能处理缩略图
                if (!_config.ThumbnailExts.Contains(ext))
                {
                    return next.Invoke(context);
                }

                var w = int.Parse(context.Request.Query["w"].FirstOrDefault() ?? "0");
                var h = int.Parse(context.Request.Query["h"].FirstOrDefault() ?? "0");

                var filePath = context.Request.Path.Value.Replace(_config.VirtualPath, _config.PhysicalPath);
                var addStr = "." + w + "_" + h + ext;
                var newPath = filePath + addStr;
                ////修改Path
                context.Request.Path = context.Request.Path + addStr;
                context.Request.QueryString = new QueryString("");

                //缩略图存在
                if (File.Exists(newPath))
                {
                    return next.Invoke(context);
                }

                //源文件不存在
                if (!File.Exists(filePath))
                {
                    context.Response.StatusCode = 404;
                    return Task.CompletedTask;
                }

                using (var image = Image.FromFile(filePath))
                {
                    using (var thumb = image.GetThumbnailImage(w, h, () => false, nint.Zero))
                    {
                        thumb.Save(newPath, ImageFormat.Jpeg);
                    }
                }

                return next.Invoke(context);
            }
            else
            {
                return next.Invoke(context);
            }
        }
    }
}