danix.steg.Steg

package danix.steg;

//Author: danix

//Digital steganographer
//Encrypts and decrypts png images
//To encrypt run java -jar Steg.jar [base] [image to hide] [output]
//To decrypt run java -jar Steg.jar [encrypted] [decrypted output]
//Works with pngs


//I give you the permission to run, edit and distribute this program
//and source code if you maintain the author tag


import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;

public class Steg {


    //Arguments:
    //3 arguments encryption: base image, secret image, encrypted filename
    public static void main(String[] args) {

        try {
            switch (args.length) {
            case 3:
                encrypt(args);
                break;
            case 2:
                decrypt(args);
                break;
            default:
                System.out.println("Argument error");
                System.out.println("Encryption: java -jar Steg.jar [base] [image to hide] [output]");
                System.out.println("Decryption: java -jar Steg.jar [encrypted] [decrypted output]");
            }
        } catch (IOException iox) {
            System.out.println(iox.getMessage());
            iox.printStackTrace(System.out);
        }
    }

    //Hides in a pixel of the original image a pixel from the hidden image
    private static int doMask(int input, int cover) {
        int mask = 0xc0c0c0c0;
        cover &= mask;
        cover >>>= 6;
        input &= ~(mask >>> 6);
        return input |= cover;
    }

    //Extracts the pixel corresponding to the hidden image in the encrypted image
    private static int extractHiddenPixel(int encrypted) {
        int mask = 0x03030303;
        encrypted &= mask;
        encrypted <<= 6;
        for (int i=0; i<3; i++)
            encrypted |= (encrypted >>> 2);
        return encrypted;
    }

    //Writes a hidden image over a base image using digital steganography
    private static void encrypt(String[] args) throws IOException {
        String base = args[0];
        String hidden = args[1];
        String output = args[2];

        BufferedImage inputImage = ImageIO.read(new File(base));
        BufferedImage hiddenImage = ImageIO.read(new File(hidden));

        if (!( (inputImage.getWidth() == hiddenImage.getWidth()) &&
             (inputImage.getHeight() == hiddenImage.getHeight()))) {
                System.out.println("Error: hidden image must have the same size as the input image!");
                System.exit(1);
        }

        int width = inputImage.getWidth();
        int height = inputImage.getHeight();

        for (int i=0; i<width; i++) {
            for (int j=0; j<height; j++) {
                int inputPixel = inputImage.getRGB(i, j);
                int hiddenPixel = hiddenImage.getRGB(i, j);
                inputPixel = doMask(inputPixel, hiddenPixel);
                inputImage.setRGB(i, j, inputPixel);
            }
        }

        if(!ImageIO.write(inputImage, "png", new File(output)))
            System.out.println("Failed writing :(");
    }

    //Reverts the process
    private static void decrypt(String[] args) throws IOException {
        String encrypted = args[0];
        String decrypted = args[1];

        BufferedImage encryptedImage = ImageIO.read(new File(encrypted));

        int width = encryptedImage.getWidth();
        int height = encryptedImage.getHeight();

        for (int i=0; i<width;i++) {
            for (int j=0; j<height; j++) {
                int encryptedPixel = encryptedImage.getRGB(i,j);
                int decryptedPixel = extractHiddenPixel(encryptedPixel);
                encryptedImage.setRGB(i, j, decryptedPixel);
            }
        }

        ImageIO.write(encryptedImage, "png", new File(decrypted));
    }



}