java 图像 大小转换

  public static  void writeImageIO(InputStream inputStream,OutputStream outputStream,int nw){
         try {
             AffineTransform transform = new AffineTransform();
             BufferedImage bis = ImageIO.read(inputStream);
             int w = bis.getWidth();
             int h = bis.getHeight();
             double scale = (double)w/h;
             int nh = (nw*h)/w ;
             double sx = (double)nw/w;
             double sy = (double)nh/h;
             transform.setToScale(sx,sy);
             System.out.println(w + " " +h);
             AffineTransformOp ato = new AffineTransformOp(transform,null);
             BufferedImage bid = new BufferedImage(nw,nh,BufferedImage.TYPE_3BYTE_BGR);
             ato.filter(bis,bid);
             ImageIO.write(bid,"jpg",outputStream);
         } catch(Exception e) {
             e.printStackTrace();
         }
    }