.Net 实现图片缩略图上传通用方法

/// <summary>    /// 生成缩略图或质量压缩    /// </summary>    /// <param name="sourcePath">源图路径（物理路径）</param>    /// <param name="targetPath">缩略图路径（物理路径）</param>    /// <param name="width">缩略图宽度，如果宽度为0则不缩略</param>    /// <param name="height">缩略图高度，如果高度为0则不缩略</param>    /// <param name="mode">生成缩略图的方式,默认为空,为空则不缩略高宽[HW 指定高宽缩放（不变形）；W 指定宽，高按比例；H 指定高，宽按比例；CUT 指定高宽裁减（不变形）]</param>     /// <param name="flag">压缩质量（数字越小压缩率越高）1-100</param>    /// <param name="size">压缩后图片的最大大小,0为不限制大小</param>    public static void MakeThumbnail(string sourcePath, string targetPath, int width = 0, int height = 0, string mode = "", int flag = 100, int size = 0)    {      Image sourceImage = null;      Image bitmap = null;      Graphics g = null;      EncoderParameters ep = null;      EncoderParameter eParam = null;      try      {        sourceImage = Image.FromFile(sourcePath);        int toWidth = 0;        if (width > 0)        {          toWidth = width;        }        else        {          toWidth = sourceImage.Width;        }        int toHeight = 0;        if (height > 0)        {          toHeight = height;        }        else        {          toHeight = sourceImage.Height;        }        int x = 0;        int y = 0;        int ow = sourceImage.Width;        int oh = sourceImage.Height;        if (width > 0 && height > 0 && !string.IsNullOrWhiteSpace(mode))        {          switch (mode.ToUpper())          {            case "HW"://指定高宽缩放（不变形）              int tempheight = sourceImage.Height * width / sourceImage.Width;              if (tempheight > height)              {                toWidth = sourceImage.Width * height / sourceImage.Height;              }              else              {                toHeight = sourceImage.Height * width / sourceImage.Width;              }              break;            case "W"://指定宽，高按比例                        toHeight = sourceImage.Height * width / sourceImage.Width;              break;            case "H"://指定高，宽按比例              toWidth = sourceImage.Width * height / sourceImage.Height;              break;            case "CUT"://指定高宽裁减（不变形）                      if ((double)sourceImage.Width / (double)sourceImage.Height > (double)toWidth / (double)toHeight)              {                oh = sourceImage.Height;                ow = sourceImage.Height * toWidth / toHeight;                y = 0;                x = (sourceImage.Width - ow) / 2;              }              else              {                ow = sourceImage.Width;                oh = sourceImage.Width * height / toWidth;                x = 0;                y = (sourceImage.Height - oh) / 2;              }              break;          }        }        //新建一个bmp图片        bitmap = new Bitmap(toWidth, toHeight);        //新建一个画板        g = Graphics.FromImage(bitmap);        g.CompositingQuality = CompositingQuality.HighQuality;        //设置高质量插值法        g.InterpolationMode = InterpolationMode.HighQualityBicubic;        //设置高质量,低速度呈现平滑程度        g.SmoothingMode = SmoothingMode.HighQuality;        //清空画布并以透明背景色填充        g.Clear(Color.Transparent);        //在指定位置并且按指定大小绘制原图片的指定部分        g.DrawImage(sourceImage, new Rectangle(0, 0, toWidth, toHeight),          new Rectangle(x, y, ow, oh),          GraphicsUnit.Pixel);        //以下代码为保存图片时，设置压缩质量        ep = new EncoderParameters();        long[] qy = new long[1];        qy[0] = flag;//设置压缩的比例1-100        eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);        ep.Param[0] = eParam;        ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();//获取图像编码器的信息        ImageCodecInfo jpegICIinfo = null;        for (int i = 0; i < arrayICI.Length; i++)        {          if (arrayICI[i].FormatDescription.Equals("JPEG"))          {            jpegICIinfo = arrayICI[i];            break;          }        }        if (jpegICIinfo != null)        {          bitmap.Save(targetPath, jpegICIinfo, ep);          FileInfo fiTarget = new FileInfo(targetPath);          if (size > 0 && fiTarget.Length > 1024 * size)          {            flag = flag - 10;            MakeThumbnail(sourcePath, targetPath, width, height, mode, flag, size);          }        }        else        {          //以jpg格式保存缩略图          bitmap.Save(targetPath, ImageFormat.Jpeg);        }      }      catch (System.Exception ex)      {        throw ex;      }      finally      {        if (sourceImage != null)        {          sourceImage.Dispose();        }        if (bitmap != null)        {          bitmap.Dispose();        }        if (g != null)        {          g.Dispose();        }        if (ep != null)        {          ep.Dispose();        }        if (eParam != null)        {          eParam.Dispose();        }      }    }