ImageIO 图片文件转换文件流

ByteArrayOutputStream bs = new ByteArrayOutputStream();
BufferedImage bufferedImage=....逻辑...;
        ImageOutputStream imOut;
        try {
            imOut = ImageIO.createImageOutputStream(bs);
            ImageIO.write(bufferedImage, "PNG", imOut);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        InputStream is = new ByteArrayInputStream(bs.toByteArray());