如果您尝试将图像保存到文件，请尝试：

If you are trying to save the image to a file try:

ImageIO.write(thumb, "jpeg", new File(....));

如果您只想要字节，请尝试执行写入调用，但是传递一个ByteArrayOutputStream，然后您可以得到字节数组，并根据需要进行操作。

If you just want at the bytes try doing the write call but pass it a ByteArrayOutputStream which you can then get the byte array out of and do with it what you want.