How to determine if a file is an image

To judge whether a file is a picture, it is not comprehensive to judge only by the suffix name. If the suffix of a txt file is changed to gif, it will be regarded as a picture, and java can judge whether the file itself is a picture, which can prevent the Trojan horse virus disguised as a picture. When uploading images, limit the upload file size to prevent impact on server availability. 

 

package com.tx.img;

 

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 IsImageFile {

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

        File file=new File("D:\\java_work\\img\\Firefox.png");  

        System.out.println(isImageFile(file));  

   }  

 

   public static boolean isImageFile(File file) {  

       ImageInputStream iis = null;  

       try {  

           iis = ImageIO.createImageInputStream(file); // resFile is to be  

           Iterator<ImageReader> iter = ImageIO.getImageReaders(iis);  

           if (!iter.hasNext()) {// The file is not a picture  

               System.out.println("This file is not a picture file");  

               return false;  

           }  

           iis.close();  

       } catch (IOException e) {  

           e.printStackTrace ();  

       }  

       return true;  

   }  

 

}