BMPHider

BMPHider.java

package com.yoavst.hacking;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

public class BMPHider {
    private static byte[] toBitArray(byte[] arr) {
        byte[] bitArray = new byte[arr.length * 8];
        for (int i = 0; i < arr.length; i++) {
            byte b = arr[i];
            for (int p = 0; p < 8; p++) {
                bitArray[i * 8 + p] = (byte) (getBit(b, p));
            }
        }
        return bitArray;
    }

    private static byte[] toByteArray(byte[] arr) {
        byte[] byteArray = new byte[arr.length / 8];
        try {
            for (int i = 0; i < arr.length; i++) {
                byte b = 0;
                for (int p = 0; p < 8; p++) {
                    b = setBit(b, p, arr[i*8+p]);
                }
                byteArray[i] = b;
            }
        } catch (ArrayIndexOutOfBoundsException ignored) {}
        return byteArray;
    }

    static void hideIn(File input, File output, String text) {
        try {
            BufferedImage img = ImageIO.read(input);
            byte[] data = toBitArray(text.getBytes(Charset.forName("ascii")));
            int p = 0;
            loop:
            for (int w = 0; w < img.getWidth(); w++) {
                for (int h = 0; h < img.getHeight(); h++) {
                    if (p >= data.length) {
                        break loop;
                    }
                    int realRGB = img.getRGB(w, h);
                    byte b = data[p];
                    if (b == 1) {
                        realRGB |= 1;
                    } else {
                        realRGB &= ~0b1;
                    }
                    img.setRGB(w, h, realRGB);
                    p++;
                }
            }
            ImageIO.write(img, "bmp", output);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    static String getHidden(File output) {
        try {
            BufferedImage img = ImageIO.read(output);
            List<Byte> bitArray = new ArrayList<>();
            for (int w = 0; w < img.getWidth(); w++) {
                for (int h = 0; h < img.getHeight(); h++) {
                    int pixel = img.getRGB(w, h);
                    byte value = (byte) (pixel & 1);
                    bitArray.add(value);
                }
            }
            return new String(toByteArray(to(bitArray)), Charset.forName("ascii"));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    private static byte[] to(List<Byte> byteList) {
        byte[] byteArray = new byte[byteList.size()];
        for (int index = 0; index < byteList.size(); index++) {
            byteArray[index] = byteList.get(index);
        }
        return byteArray;
    }

    private static int getBit(byte b, int position) {
        return ((b >> position) & 1);
    }

    private static byte setBit(byte b, int pos, int value) {
        if (value == 1) {
            return (byte) (b | (1 << pos));
        } else {
            return (byte) (b & ~(1 << pos));
        }
    }
}