java後臺壓縮圖片

public FileEntry getThumbnailFile(FileEntry fileEntry, String fileName, String contentType)
  {
    try
    {
      Image image = ImageIO.read(fileEntry.getFile());
      // 為等比縮放計算輸出的圖片寬度及高度
      double rate1 = ((double) image.getWidth(null)) / (double) outputWidth + 0.1;
      double rate2 = ((double) image.getHeight(null)) / (double) outputHeight + 0.1;
      // 根據縮放比率大的進行縮放控制
      double rate = rate1 > rate2 ? rate1 : rate2;
      int newWidth = (int) (((double) image.getWidth(null)) / rate);
      int newHeight = (int) (((double) image.getHeight(null)) / rate);

      // SCALE_SMOOTH 的縮略演算法 生成縮圖片的平滑度的 優先順序比速度高 生成的圖片質量比較好 但速度慢
      BufferedImage tag = new BufferedImage((int) newWidth, (int) newHeight, BufferedImage.TYPE_INT_RGB);
      // 繪製縮小後的圖
      tag.getGraphics().drawImage(image, 0, 0, newWidth, newHeight, null);
      // File destFile = new File("C:\\temp\\456.jpg");
      // FileOutputStream out = new FileOutputStream(destFile); // 輸出到檔案流
      UUID fileId = UUID.randomUUID();
      File file = this.getFileById(fileId, true);
      FileOutputStream out = new FileOutputStream(file);
      // 可以正常實現bmp、png、gif轉jpg
      JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
      encoder.encode(tag); // JPEG編碼
      out.close();
      return new FileEntry(fileId, file, fileName, contentType);
    }
    catch (Throwable t)
    {
      return fileEntry;
    }
  }