给上传的文件生成缩略图（图片和视频）

备注：里面用到的ffmpeg可在https://ffmpeg.zeranoe.com/builds/ 下载


1、根据视频，生成截图

#region 从视频画面中截取一帧画面为图片
        /// <summary>
        /// 从视频画面中截取一帧画面为图片
        /// </summary>
        /// <param name="VideoName">视频文件，绝对路径</param>
        /// <param name="WidthAndHeight">图片的尺寸如:240*180</param>
        /// <param name="CutTimeFrame">开始截取的时间如:"1"</param>
        /// <returns></returns>
        public static string GetPicFromVideo(string VideoName, string WidthAndHeight, string CutTimeFrame)
        {
            //ffmpeg执行文件的路径
            string ffmpeg = System.AppDomain.CurrentDomain.BaseDirectory + "ffmpeg\\ffmpeg.exe";
            string PicName = VideoName + ".jpg";//视频图片的名字，绝对路径
            System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo(ffmpeg);
            startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
            startInfo.Arguments = " -i " + VideoName
                                + " -y -f image2 -ss " + CutTimeFrame
                                + " -t 0.001 -s " + WidthAndHeight
                                + " " + PicName;  //設定程式執行參數
            try
            {
                System.Diagnostics.Process.Start(startInfo);
                Thread.Sleep(5000);//线程挂起，等待ffmpeg截图完毕
            }
            catch (Exception e)
            {
                return e.Message;
            }

            //返回视频图片完整路径
            if (System.IO.File.Exists(PicName))
                return PicName;
            return "";
        }
        #endregion

2、图片压缩并保存GetPicThumbnail

#region 图片压缩并保存GetPicThumbnail
        /// <summary>
        /// 无损压缩图片
        /// </summary>
        /// <param name="sFile">原文件位置</param>
        /// <param name="dFile">压缩后保存位置</param>
        /// <param name="flag">压缩比例，eg:按照百分比算如80，就是原图的高度乘以80%</param>
        /// <returns></returns>
        public static bool GetPicThumbnail(string sFile, string dFile, int flag)
        {
            System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);
            ImageFormat tFormat = iSource.RawFormat;
            int sW = 0, sH = 0;
            //按比例缩放
            Size tem_size = new Size(iSource.Width, iSource.Height);
            int dHeight = iSource.Height * flag / 100; //高度压缩百分不
            int dWidth = iSource.Width * flag / 100;//宽度压缩百分比
            if (tem_size.Width > dHeight || tem_size.Width > dWidth) //将**改成c#中的或者操作符号
            {
                if ((tem_size.Width * dHeight) > (tem_size.Height * dWidth))
                {
                    sW = dWidth;
                    sH = (dWidth * tem_size.Height) / tem_size.Width;
                }
                else
                {
                    sH = dHeight;
                    sW = (tem_size.Width * dHeight) / tem_size.Height;
                }
            }
            else
            {
                sW = tem_size.Width;
                sH = tem_size.Height;
            }

            Bitmap ob = new Bitmap(dWidth, dHeight);
            Graphics g = Graphics.FromImage(ob);
            g.Clear(Color.WhiteSmoke);
            g.CompositingQuality = CompositingQuality.HighQuality;
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);
            g.Dispose();
            //以下代码为保存图片时，设置压缩质量
            EncoderParameters ep = new EncoderParameters();
            long[] qy = new long[1];
            qy[0] = flag;//设置压缩的比例1-100
            EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
            ep.Param[0] = eParam;
            try
            {
                ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();

                ImageCodecInfo jpegICIinfo = null;

                for (int x = 0; x < arrayICI.Length; x++)
                {
                    if (arrayICI[x].FormatDescription.Equals("JPEG"))
                    {
                        jpegICIinfo = arrayICI[x];
                        break;
                    }
                }
                if (jpegICIinfo != null)
                {
                    ob.Save(dFile, jpegICIinfo, ep);//dFile是压缩后的新路径
                }
                else
                {
                    ob.Save(dFile, tFormat);
                }
                return true;
            }
            catch
            {
                return false;
            }
            finally
            {
                iSource.Dispose();
                ob.Dispose();

            }
        }
        #endregion

3、循环文件夹中的所有文件，生成对应的压缩图片   需要用到循环调用
先调用获取目录下所有文件夹的方法，此方法中调用了getFileName方法，也调用了自己，可实现循环遍历直到把所有文件都执行一边

#region 获取指定路径下所有文件名
        /// <summary>
        /// 获得指定路径下所有文件名
        /// </summary>
        /// <param name="path">文件写入流</param>
        public static void getFileName(string path)
        {
            string filePath = string.Empty;
            string newFilePath = string.Empty;
            DirectoryInfo root = new DirectoryInfo(path);
            FileInfo[] files = root.GetFiles();
            foreach (FileInfo f in files)
            {
                filePath = f.FullName;  //完整的目录名 
                newFilePath = filePath.Replace("D:\\DataImgs", "D:\\DataImgs\\thumbnail");
                if (f.Name.ToLower().Contains("mp4") || f.Name.ToLower().Contains("avi") || f.Name.ToLower().Contains("rmvb"))
                {
                    //针对MP4，把第一帧存为图片
                    GetPicFromVideo(filePath, "100*160", "1", ffmpeg);
                }
                else
                {
                    //如果是图片都放到thumbnail文件夹下
                    GetPicThumbnail(filePath, newFilePath, 40);
                }
            }
        }
        #endregion

        #region 获取指定路径下所有子目录名
        /// <summary>
        /// 获得指定路径下所有子目录名
        /// </summary>
        /// <param name="path">文件夹路径</param>
        /// <param name="indent">输出时的缩进量</param>
        public static void getDirectory(string path)
        {
            getFileName(path);
            string dirPath = string.Empty;
            string newDirPath = string.Empty;
            DirectoryInfo root = new DirectoryInfo(path);
            DirectoryInfo[] dirs = root.GetDirectories();
            foreach (DirectoryInfo d in dirs)
            {
                dirPath = d.FullName;
                if (dirPath == "D:\\DataImgs\\thumbnail")
                {
                    MessageBox.Show("操作完成！");
                }
                else
                {
                    newDirPath = dirPath.Replace("D:\\DataImgs", "D:\\DataImgs\\thumbnail");  //更换文件夹创建路径
                    if (!Directory.Exists(newDirPath))   //如果不存在，则创建此文件夹
                    {
                        Directory.CreateDirectory(newDirPath);
                    }
                    getDirectory(dirPath);
                }
            }
        }
        #endregion

有了这几个文件，批量压缩或者单独在上传时压缩又能游刃有余了