code: public static void gray(InputStream srcStream, OutputStream destStream) {
  		gray(read(srcStream), getImageOutputStream(destStream));
  	}
docs: 彩色转为黑白<br>
  此方法并不关闭流
  
  @param srcStream 源图像流
  @param destStream 目标图像流
  @since 3.0.9