java使用ImageReader判断图片的类型

package com.javacodegeeks.snippets.desktop;

import java.io.File;
import java.io.IOException;
import java.util.Iterator;

import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import javax.imageio.stream.ImageInputStream;

public class DetermineFormatOfAnImage {

public static void main(String[] args) throws IOException {

// get image format in a file
File file = new File("newimage.jpg");

// create an image input stream from the specified file
ImageInputStream iis = ImageIO.createImageInputStream(file);

// get all currently registered readers that recognize the image format
Iterator<ImageReader> iter = ImageIO.getImageReaders(iis);

if (!iter.hasNext()) {
throw new RuntimeException("No readers found!");
}

// get the first reader
ImageReader reader = iter.next();

System.out.println("Format: " + reader.getFormatName());

// close stream
iis.close();

}

}