java使用ImageReader判断图片的类型详解编程语言

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(); 
 
    } 
 
}