java中判断文件是否是图片，不是用扩展名
来源于网络资源，太多出处了，不知道哪个是原创，- -!
/** * 检查传入file的format名称 * @param f 传入的文件 * @return */ public static String getFormatInFile(File f) { return getFormatName(f); } /** * 对文件进行format检索 * .jpg .jpeg .jpe .jfif ===> JPEG * .png ===> png * .gif ===> gif * . * @param o * @return */ // Returns the format name of the image in the object 'o'. // Returns null if the format is not known. 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; }