简单映射文件名

    public String rename(String s) throws NoSuchAlgorithmException {
        MessageDigest md5 = MessageDigest.getInstance("MD5");
        byte[] digest = md5.digest(s.getBytes(StandardCharsets.UTF_8));
        StringBuilder sb = new StringBuilder();
        for (int i=0; i< digest.length; i++) {
            sb.append(Integer.toHexString(0xff & digest[i]));
        }
        sb.append(".jpg");
        return sb.toString();
    }

调整图片大小

   public void resizeImg(InputStream is, OutputStream os, String formatName) throws IOException {
        int width = 55;
        int height = 50;
        BufferedImage img = ImageIO.read(is);

        BufferedImage nImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics = nImg.createGraphics();
        graphics.drawImage(img, 0, 0, width, height, null);
        ImageIO.write(nImg, formatName, os);

        is.close();
        os.flush();
        os.close();
    }

main函数

public void static main() throws NoSuchAlgorithmException, IOException {
        String spath = "D:\\";
        String tpath = "E:\\";
    
        File nPath = new File(spath);

        if (nPath.isDirectory()) {
            // 读取文件目录下所有文件
            File[] files = nPath.listFiles();

            for (int i=0; i< files.length; i++) {
                String name = files[i].getName();
                InputStream is = new FileInputStream(files[i]);
                File file = new File(tpath + name);
                OutputStream os = new FileOutputStream(file);
                resizeImg(is, os, "jpg");
            }
        }
}