Java如何实现bmp和jpeg图片格式互转

public static String bmp2Jpeg(String filePath, String outPath) {
    try {
        long start = System.currentTimeMillis();
        // 加载bmp图片
        File file = new File(filePath);
        Image img = ImageIO.read(file);
        BufferedImage tag = new BufferedImage(img.getWidth(null), img.getHeight(null), BufferedImage.TYPE_INT_RGB);
        tag.getGraphics().drawImage(img.getScaledInstance(img.getWidth(null), img.getHeight(null), Image.SCALE_SMOOTH), 0, 0, null);

        // 输出为Jpeg
        FileOutputStream out = new FileOutputStream(outPath);
        // JPEGImageEncoder可适用于其他图片类型的转换
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
        encoder.encode(tag);
        out.close();
        
        log.info("bmp 转 JPEG，共耗时：  " + (System.currentTimeMillis() - start) + " 毫秒");
        return outPath;
    } catch (IOException e) {
        e.printStackTrace();
    }
        return outPath;
    }

public static void jpeg2Bmp(String inputPath, String outputPath) {
    try {
        long start = System.currentTimeMillis();
    
        // 加载Jpeg图片资源
        FileImageInputStream fiis = new FileImageInputStream(new File(inputPath));
        FileImageOutputStream fios = new FileImageOutputStream(new File(outputPath));
        ImageReader jpegReader = null;
        Iterator<ImageReader> it1 = ImageIO.getImageReadersByFormatName("jpeg");
        if (it1.hasNext()) {
            jpegReader = it1.next();
        }
        jpegReader.setInput(fiis);
        
        ImageWriter bmpWriter = null;
        Iterator<ImageWriter> it2 = ImageIO.getImageWritersByFormatName("bmp");
        if (it2.hasNext()) {
            bmpWriter = it2.next();
        }
        bmpWriter.setOutput(fios);
        BufferedImage br = jpegReader.read(0);
        bmpWriter.write(br);
        fiis.close();
        fios.close();
        
        log.info("jpeg 转 bmp，共耗时：" + (System.currentTimeMillis() - start) + " 毫秒");
    } catch (IOException e) {
        e.printStackTrace();
    }
}