Thread: java.lang.IllegalArgumentException: im == null!

I am getting the following output after executing the attached code:

Available: 109980
Reader is not found
Image is NULL
java.lang.IllegalArgumentException: im == null!
at javax.imageio.ImageIO.write(Unknown Source)
at javax.imageio.ImageIO.write(Unknown Source)
at Main_TEST.main(Main_TEST.java:48)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknow n Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Un known Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.ru nCommand(JavacCompiler.java:271)

Can anyone please give me a solution to this problem, or can anyone suggest me any alternative ways to write image after bit-manipulation.

Thanks in advance in anticipation of an early reply.

import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import java.io.*;
import java.util.Iterator;
 
public class Main_TEST {
    public static void main(String[] args) {
        try{
            //String fileName=new File();
            BufferedImage img = ImageIO.read(new File("C:\\test.jpg"));
            BufferedImage new_img=new BufferedImage(img.getWidth(), img.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
 
            Graphics2D g=new_img.createGraphics();
 
            g.drawRenderedImage(img, null);
            g.dispose();
 
            //convert BufferedImage to byte array
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ImageIO.write( new_img, "jpg", baos );
            baos.flush();
            byte[] imageInByte = baos.toByteArray();
 
            //call to steg_process method..
            byte[] output_data=steg_process(imageInByte);
 
            //convert byte array back to BufferedImage
            InputStream in = new ByteArrayInputStream(output_data);
//if output_data is replaced by imageInByte and previous line is commented out then new image is created
 
            System.out.println("Available: "+in.available());
 
            new_img = ImageIO.read(in);
//FileInputStream inp=new FileInputStream(new File(fileName));
            Iterator i=ImageIO.getImageReaders(in);
            if(i.hasNext()){
                System.out.println("Reader is found");
            }else{
                System.out.println("Reader is not found");
            }            
 
            if(new_img==null){
                System.out.println("Image is NULL");
            }
 
            File outputfile = new File("saved.jpg");
            ImageIO.write(new_img, "jpg", outputfile);             
 
        }catch(IOException e){
            e.printStackTrace();
        }
    }
    // This method is for manipulating byte[] array, change some of it's bits and then return the modified byte[]
    private static byte[] steg_process(byte[] orig_data){        
        byte a=0;
        orig_data[0]=a;        
        return orig_data;
    }
}