C# 图片生成缩略图

C# 图片生成缩略图方法：

 /// <summary>
 /// 生成缩略图
 /// </summary>
 /// <param name="fileName">原图路径</param>
 /// <param name="newFile">缩略图路径</param>
 /// <param name="maxHeight">最大高度</param>
 /// <param name="maxWidth">最大宽度</param>
 public string ThumbnailImage(string fileName, string newFile, int maxHeight, int maxWidth)
 {
     System.Drawing.Image img = System.Drawing.Image.FromFile(fileName);
     System.Drawing.Imaging.ImageFormat thisFormat = img.RawFormat;
     //缩略图尺寸
     double w = 0.0;                              //图片的宽
     double h = 0.0;                              //图片的高
     double sw = Convert.ToDouble(img.Width);
     double sh = Convert.ToDouble(img.Height);
     double mw = Convert.ToDouble(maxWidth);
     double mh = Convert.ToDouble(maxHeight);
     if (sw < mw && sh < mh)
     {
         w = sw;
         h = sh;
     }
     else if ((sw / sh) > (mw / mh))
     {
         w = maxWidth;
         h = (w * sh) / sw;
     }
     else
     {
         h = maxHeight;
         w = (h * sw) / sh;
     }
     Size newSize = new Size(Convert.ToInt32(w), Convert.ToInt32(h));
     Bitmap outBmp = new Bitmap(newSize.Width, newSize.Height);
     Graphics g = Graphics.FromImage(outBmp);
     //设置画布的描绘质量
     g.CompositingQuality = CompositingQuality.HighQuality;
     g.SmoothingMode = SmoothingMode.HighQuality;
     g.InterpolationMode = InterpolationMode.HighQualityBicubic;
     g.DrawImage(img, new Rectangle(, , newSize.Width, newSize.Height), , , img.Width, img.Height, GraphicsUnit.Pixel);
     g.Dispose();
     //以下代码为保存图片时,设置压缩质量
     EncoderParameters encoderParams = new EncoderParameters();
     long[] quality = new long[];
     quality[] = ;
     EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);
     encoderParams.Param[] = encoderParam;
     //获得包含有关内置图像编码解码器的信息的ImageCodecInfo 对象.
     ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
     ImageCodecInfo jpegICI = null;
     for (int x = ; x < arrayICI.Length;x++)
     {
         if (arrayICI[x].FormatDescription.Equals("JPEG"))
         {
             jpegICI = arrayICI[x];
             //设置JPEG编码
             break;
         }
      }
      if (jpegICI != null)
      {
          Bitmap newbit = new Bitmap(outBmp);
          newbit.Save(newFile, jpegICI, encoderParams);
      }
      else
      {
          outBmp.Save(newFile,
          thisFormat);
      }
      img.Dispose();
      outBmp.Dispose();
      return newFile;
 }