一.MultipartFile
picture.transferTo(file);
//picture(MultipartFile類型),file(File類型)(上傳的路徑+文件名)
二.ImageIO
BufferedImage image = new BufferedImage(width_pic, height_pic, BufferedImage.TYPE_INT_ARGB);
File file = new File(path);
ImageIO.write(image, "png", file);