/** * 图片判断 */private static String getFormatName(Object o) {       try {           // Create an image input stream on the image           ImageInputStream iis = ImageIO.createImageInputStream(o);             // Find all image readers that recognize the image format           Iterator<ImageReader> iter = ImageIO.getImageReaders(iis);           if (!iter.hasNext()) {               // No readers found               return null;           }             // Use the first reader           ImageReader reader = (ImageReader) iter.next();             // Close stream           iis.close();             // Return the format name           return reader.getFormatName();       } catch (IOException e) {           //       }     // The image could not be read       return null;   }