Question

Write a Java program that can embed and extract a simple text message into a chosen PNG image. The program should also allow extraction of the message from the stegotext image. In particular, the program should do the following:

1. Prompts user to enter a choice of PNG image to hide a text message.

2. Prompts user to enter the text message that is to be hidden.

3. Create a modified image after hiding the text message (as explained above) and save the image as a new PNG picture.

4. Display the hidden message when a PNG image is supplied. [For testing purpose, the user may choose to use a different image file that already has a message hidden into it following the above scheme.]

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A sample Java code (PixelData.java) is provided to give an idea how to get R, G, B values of a pixel in a PNG image. You can build on that, but you need to explore BufferedImage class, Color class, ImageIO package in JavaFX, getRGB(), setRGB() methods etc.from Java API.

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Here's the PixelData.java code:

import java.util.*;
import java.io.*;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;

public class PixelBits {

public static void main(String[] args) {
  
Scanner input = new Scanner(System.in);
System.out.print("Enter the input image file name (with .png extension): ");
String file = input.next();

BufferedImage img;

try {
img = ImageIO.read(new File(file));
// There is a method ImageIO.write() to create a
// picture file from a BufferedImage object
  
int h = img.getHeight();
int w = img.getWidth();
int totalpixel = h*w;
System.out.println("\n Image height = " + h + " and Image width = " + w);
System.out.println(" Total number of pixels = " + totalpixel);
  
System.out.println("\n In each pixel you have 3 components, R-G-B.\n Hence you can embed 3 bits in each pixel.");
System.out.println("\n Total number of bits that can be embedded in the picture = " + totalpixel*3);
System.out.println("\n Total number of ASCII characters that can be embedded = " + (totalpixel*3)/8);
  
// store each pixel's RGB values
int[][] pixelData = new int[h*w][3];
int[] rgb;

int numberOfPixels = 0;
for(int i = 0; i < h; i++){
for(int j = 0; j < w; j++){
rgb = PixelData(img, j, i);

for(int k = 0; k < rgb.length; k++){
pixelData[numberOfPixels][k] = rgb[k];
}

numberOfPixels++;
}
}

} catch (IOException e) {
e.printStackTrace();
}

}

private static int[] PixelData(BufferedImage img, int x, int y) {
int argb = img.getRGB(x, y);
  
int[] rgb = new int[3];
rgb[0] = (argb >> 16) & 0xff; //Red
rgb[1] = (argb >> 8) & 0xff; // Green
rgb[2] = (argb) & 0xff; // Blue

// 0xff is Hex for 255 and used as a mask to get last 8 bits of a bit string

// Remove the comment from the next line if you want to display RGB values for all pixels.
// Caution: There can be too many pixels to display. So use it if absolutely necessary.

//System.out.println("Red: " + rgb[0] + ", Green: " + rgb[1] + ", Blue: " + rgb[2]);
return rgb;
}

}

Answer 1

import java.awt.Component;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import java.util.Scanner;

public class Steganography extends Component {

public static void main(String[] foo) {
new JavaWalkBufferedImageTest1();
   Scanner user_input = new Scanner(System.in);
   System.out.println("Hidden Message");
   String hiddenmsg;
   hiddenmsg=user_input.next();
   byte[] bytes = hiddenmsg.getBytes();
   StringBuilder binary = new StringBuilder();
   for (byte b : bytes)
   {
       int val = b;
       for (int i = 0; i < 8; i++)
       {
           binary.append((val & 128) == 0 ? 0 : 1);
           val <<= 1;
       }
   }
   System.out.println("'" + hiddenmsg + "' to binary: " + binary);
}
  
public void printPixelARGB(int pixel) {
int red = (pixel >> 16) & 0xff;
int green = (pixel >> 8) & 0xff;
int blue = (pixel) & 0xff;
   String strBinaryNumber1 = Integer.toBinaryString(red);
   String strBinaryNumber2 = Integer.toBinaryString(green);
   String strBinaryNumber3 = Integer.toBinaryString(blue);
System.out.println("RGB (Decimal Format):" + red + ", " + green + ", " + blue);
   System.out.println("RGB (Binary Format):"+strBinaryNumber1+","+strBinaryNumber2+","+strBinaryNumber3);
   System.out.println("Last bit of RGB:" +strBinaryNumber1.substring(strBinaryNumber1.length()-1) + "," + strBinaryNumber2.substring(strBinaryNumber2.length()-1) + "," +strBinaryNumber3.substring(strBinaryNumber3.length()-1));
}
  
  

private void marchThroughImage(BufferedImage image) {
int w = image.getWidth();
int h = image.getHeight();

for (int i = 0; i < h; i++) {
for (int j = 0; j < w; j++) {
int pixel = image.getRGB(j, i);
printPixelARGB(pixel);
System.out.println("");
}
}
}

public Steganography() {
try {
// get the BufferedImage, using the ImageIO class
   System.out.println("Enter the name of the image");
   Scanner input = new Scanner(System.in);
   String imagename;
   imagename=input.next();
BufferedImage image =
ImageIO.read(this.getClass().getResource(imagename+".jpg"));
marchThroughImage(image);
} catch (IOException e) {
System.err.println(e.getMessage());
}
}}