encrypting image with AES in java

I wrote a code that encrypts an image and decrypt it and it work but the problem when i encrypt the image than Close the program and run it again to decrypt the previous encrypted image,it does not give the original image.

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

public class aes {
    private static int Nb, Nk, Nr;
    private static byte[][] w;

    private static int[] sbox = {0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F,
            0xC5, 0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76, 0xCA, 0x82,
            0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 0xAD, 0xD4, 0xA2, 0xAF, 0x9C,
            0xA4, 0x72, 0xC0, 0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC,
            0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15, 0x04, 0xC7, 0x23,
            0xC3, 0x18, 0x96, 0x05, 0x9A, 0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27,
            0xB2, 0x75, 0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 0x52,
            0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84, 0x53, 0xD1, 0x00, 0xED,
            0x20, 0xFC, 0xB1, 0x5B, 0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58,
            0xCF, 0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 0x45, 0xF9,
            0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8, 0x51, 0xA3, 0x40, 0x8F, 0x92,
            0x9D, 0x38, 0xF5, 0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,
            0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 0xC4, 0xA7, 0x7E,
            0x3D, 0x64, 0x5D, 0x19, 0x73, 0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A,
            0x90, 0x88, 0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB, 0xE0,
            0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 0xC2, 0xD3, 0xAC, 0x62,
            0x91, 0x95, 0xE4, 0x79, 0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E,
            0xA9, 0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08, 0xBA, 0x78,
            0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 0xE8, 0xDD, 0x74, 0x1F, 0x4B,
            0xBD, 0x8B, 0x8A, 0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E,
            0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E, 0xE1, 0xF8, 0x98,
            0x11, 0x69, 0xD9, 0x8E, 0x94, 0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55,
            0x28, 0xDF, 0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 0x41,
            0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16};

    private static int[] inv_sbox = {0x52, 0x09, 0x6A, 0xD5, 0x30, 0x36, 0xA5,
            0x38, 0xBF, 0x40, 0xA3, 0x9E, 0x81, 0xF3, 0xD7, 0xFB, 0x7C, 0xE3,
            0x39, 0x82, 0x9B, 0x2F, 0xFF, 0x87, 0x34, 0x8E, 0x43, 0x44, 0xC4,
            0xDE, 0xE9, 0xCB, 0x54, 0x7B, 0x94, 0x32, 0xA6, 0xC2, 0x23, 0x3D,
            0xEE, 0x4C, 0x95, 0x0B, 0x42, 0xFA, 0xC3, 0x4E, 0x08, 0x2E, 0xA1,
            0x66, 0x28, 0xD9, 0x24, 0xB2, 0x76, 0x5B, 0xA2, 0x49, 0x6D, 0x8B,
            0xD1, 0x25, 0x72, 0xF8, 0xF6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xD4,
            0xA4, 0x5C, 0xCC, 0x5D, 0x65, 0xB6, 0x92, 0x6C, 0x70, 0x48, 0x50,
            0xFD, 0xED, 0xB9, 0xDA, 0x5E, 0x15, 0x46, 0x57, 0xA7, 0x8D, 0x9D,
            0x84, 0x90, 0xD8, 0xAB, 0x00, 0x8C, 0xBC, 0xD3, 0x0A, 0xF7, 0xE4,
            0x58, 0x05, 0xB8, 0xB3, 0x45, 0x06, 0xD0, 0x2C, 0x1E, 0x8F, 0xCA,
            0x3F, 0x0F, 0x02, 0xC1, 0xAF, 0xBD, 0x03, 0x01, 0x13, 0x8A, 0x6B,
            0x3A, 0x91, 0x11, 0x41, 0x4F, 0x67, 0xDC, 0xEA, 0x97, 0xF2, 0xCF,
            0xCE, 0xF0, 0xB4, 0xE6, 0x73, 0x96, 0xAC, 0x74, 0x22, 0xE7, 0xAD,
            0x35, 0x85, 0xE2, 0xF9, 0x37, 0xE8, 0x1C, 0x75, 0xDF, 0x6E, 0x47,
            0xF1, 0x1A, 0x71, 0x1D, 0x29, 0xC5, 0x89, 0x6F, 0xB7, 0x62, 0x0E,
            0xAA, 0x18, 0xBE, 0x1B, 0xFC, 0x56, 0x3E, 0x4B, 0xC6, 0xD2, 0x79,
            0x20, 0x9A, 0xDB, 0xC0, 0xFE, 0x78, 0xCD, 0x5A, 0xF4, 0x1F, 0xDD,
            0xA8, 0x33, 0x88, 0x07, 0xC7, 0x31, 0xB1, 0x12, 0x10, 0x59, 0x27,
            0x80, 0xEC, 0x5F, 0x60, 0x51, 0x7F, 0xA9, 0x19, 0xB5, 0x4A, 0x0D,
            0x2D, 0xE5, 0x7A, 0x9F, 0x93, 0xC9, 0x9C, 0xEF, 0xA0, 0xE0, 0x3B,
            0x4D, 0xAE, 0x2A, 0xF5, 0xB0, 0xC8, 0xEB, 0xBB, 0x3C, 0x83, 0x53,
            0x99, 0x61, 0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26, 0xE1,
            0x69, 0x14, 0x63, 0x55, 0x21, 0x0C, 0x7D};

    private static int Rcon[] = {0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
            0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39,
            0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a,
            0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
            0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef,
            0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc,
            0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b,
            0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
            0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94,
            0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20,
            0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35,
            0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f,
            0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
            0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63,
            0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd,
            0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb};
    private static String key;

    public static byte[] keygeneration() throws Exception {
        key = "ffffffffaaaaaaaa";
        return key.getBytes();

    }

    private static byte[] xor_func(byte[] a, byte[] b) {
        byte[] out = new byte[a.length];
        for (int i = 0; i < a.length; i++) {
            out[i] = (byte) (a[i] ^ b[i]);
        }
        return out;

    }

    private static byte[][] generateSubkeys(byte[] key) {
        byte[][] tmp = new byte[Nb * (Nr + 1)][4];

        int i = 0;
        while (i < Nk) {

            tmp[i][0] = key[i * 4];
            tmp[i][1] = key[i * 4 + 1];
            tmp[i][2] = key[i * 4 + 2];
            tmp[i][3] = key[i * 4 + 3];
            i++;
        }
        i = Nk;
        while (i < Nb * (Nr + 1)) {
            byte[] temp = new byte[4];
            for (int k = 0; k < 4; k++)
                temp[k] = tmp[i - 1][k];
            if (i % Nk == 0) {
                temp = SubWord(rotateWord(temp));
                temp[0] = (byte) (temp[0] ^ (Rcon[i / Nk] & 0xff));
            } else if (Nk > 6 && i % Nk == 4) {
                temp = SubWord(temp);
            }
            tmp[i] = xor_func(tmp[i - Nk], temp);
            i++;
        }

        return tmp;
    }

    private static byte[] SubWord(byte[] in) {
        byte[] tmp = new byte[in.length];

        for (int i = 0; i < tmp.length; i++)
            tmp[i] = (byte) (sbox[in[i] & 0x000000ff] & 0xff);

        return tmp;
    }

    private static byte[] rotateWord(byte[] input) {
        byte[] tmp = new byte[input.length];
        tmp[0] = input[1];
        tmp[1] = input[2];
        tmp[2] = input[3];
        tmp[3] = input[0];

        return tmp;
    }

    private static byte[][] AddRoundKey(byte[][] state, byte[][] w, int round) {

        byte[][] tmp = new byte[state.length][state[0].length];

        for (int c = 0; c < Nb; c++) {
            for (int l = 0; l < 4; l++)
                tmp[l][c] = (byte) (state[l][c] ^ w[round * Nb + c][l]);
        }

        return tmp;
    }

    private static byte[][] SubBytes(byte[][] state) {

        byte[][] tmp = new byte[state.length][state[0].length];
        for (int row = 0; row < 4; row++)
            for (int col = 0; col < Nb; col++)
                tmp[row][col] = (byte) (sbox[(state[row][col] & 0x000000ff)] & 0xff);

        return tmp;
    }

    private static byte[][] InvSubBytes(byte[][] state) {
        for (int row = 0; row < 4; row++)
            for (int col = 0; col < Nb; col++)
                state[row][col] = (byte) (inv_sbox[(state[row][col] & 0x000000ff)] & 0xff);

        return state;
    }

    private static byte[][] ShiftRows(byte[][] state) {

        byte[] t = new byte[4];
        for (int r = 1; r < 4; r++) {
            for (int c = 0; c < Nb; c++)
                t[c] = state[r][(c + r) % Nb];
            for (int c = 0; c < Nb; c++)
                state[r][c] = t[c];
        }

        return state;
    }

    private static byte[][] InvShiftRows(byte[][] state) {
        byte[] t = new byte[4];
        for (int r = 1; r < 4; r++) {
            for (int c = 0; c < Nb; c++)
                t[(c + r) % Nb] = state[r][c];
            for (int c = 0; c < Nb; c++)
                state[r][c] = t[c];
        }
        return state;
    }

    private static byte[][] InvMixColumns(byte[][] s) {
        int[] sp = new int[4];
        byte b02 = (byte) 0x0e, b03 = (byte) 0x0b, b04 = (byte) 0x0d, b05 = (byte) 0x09;
        for (int c = 0; c < 4; c++) {
            sp[0] = FFMul(b02, s[0][c]) ^ FFMul(b03, s[1][c]) ^ FFMul(b04, s[2][c]) ^ FFMul(b05, s[3][c]);
            sp[1] = FFMul(b05, s[0][c]) ^ FFMul(b02, s[1][c]) ^ FFMul(b03, s[2][c]) ^ FFMul(b04, s[3][c]);
            sp[2] = FFMul(b04, s[0][c]) ^ FFMul(b05, s[1][c]) ^ FFMul(b02, s[2][c]) ^ FFMul(b03, s[3][c]);
            sp[3] = FFMul(b03, s[0][c]) ^ FFMul(b04, s[1][c]) ^ FFMul(b05, s[2][c]) ^ FFMul(b02, s[3][c]);
            for (int i = 0; i < 4; i++) s[i][c] = (byte) (sp[i]);
        }

        return s;
    }

    private static byte[][] MixColumns(byte[][] s) {
        int[] sp = new int[4];
        byte b02 = (byte) 0x02, b03 = (byte) 0x03;
        for (int c = 0; c < 4; c++) {
            sp[0] = FFMul(b02, s[0][c]) ^ FFMul(b03, s[1][c]) ^ s[2][c] ^ s[3][c];
            sp[1] = s[0][c] ^ FFMul(b02, s[1][c]) ^ FFMul(b03, s[2][c]) ^ s[3][c];
            sp[2] = s[0][c] ^ s[1][c] ^ FFMul(b02, s[2][c]) ^ FFMul(b03, s[3][c]);
            sp[3] = FFMul(b03, s[0][c]) ^ s[1][c] ^ s[2][c] ^ FFMul(b02, s[3][c]);
            for (int i = 0; i < 4; i++) s[i][c] = (byte) (sp[i]);
        }

        return s;
    }

    public static byte FFMul(byte a, byte b) {
        byte aa = a, bb = b, r = 0, t;
        while (aa != 0) {
            if ((aa & 1) != 0)
                r = (byte) (r ^ bb);
            t = (byte) (bb & 0x80);
            bb = (byte) (bb << 1);
            if (t != 0)
                bb = (byte) (bb ^ 0x1b);
            aa = (byte) ((aa & 0xff) >> 1);
        }
        return r;
    }

    public static byte[] encryptBloc(byte[] in) {
        byte[] tmp = new byte[in.length];


        byte[][] state = new byte[4][Nb];

        for (int i = 0; i < in.length; i++)
            state[i / 4][i % 4] = in[i % 4 * 4 + i / 4];

        state = AddRoundKey(state, w, 0);
        for (int round = 1; round < Nr; round++) {
            state = SubBytes(state);
            state = ShiftRows(state);
            state = MixColumns(state);
            state = AddRoundKey(state, w, round);
        }
        state = SubBytes(state);
        state = ShiftRows(state);
        state = AddRoundKey(state, w, Nr);

        for (int i = 0; i < tmp.length; i++)
            tmp[i % 4 * 4 + i / 4] = state[i / 4][i % 4];

        return tmp;
    }

    public static byte[] decryptBloc(byte[] in) {
        byte[] tmp = new byte[in.length];

        byte[][] state = new byte[4][Nb];

        for (int i = 0; i < in.length; i++)
            state[i / 4][i % 4] = in[i % 4 * 4 + i / 4];

        state = AddRoundKey(state, w, Nr);
        for (int round = Nr - 1; round >= 1; round--) {
            state = InvSubBytes(state);
            state = InvShiftRows(state);
            state = AddRoundKey(state, w, round);
            state = InvMixColumns(state);

        }
        state = InvSubBytes(state);
        state = InvShiftRows(state);
        state = AddRoundKey(state, w, 0);

        for (int i = 0; i < tmp.length; i++)
            tmp[i % 4 * 4 + i / 4] = state[i / 4][i % 4];

        return tmp;
    }

    public static byte[] encrypt(byte[] in, byte[] key) {

        Nb = 4;
        Nk = key.length / 4;
        Nr = Nk + 6;


        int lenght = 0;
        byte[] padding = new byte[1];
        int i;
        lenght = 16 - in.length % 16;
        padding = new byte[lenght];
        padding[0] = (byte) 0x80;

        for (i = 1; i < lenght; i++)
            padding[i] = 0;

        byte[] tmp = new byte[in.length + lenght];
        byte[] bloc = new byte[16];


        w = generateSubkeys(key);

        int count = 0;

        for (i = 0; i < in.length + lenght; i++) {
            if (i > 0 && i % 16 == 0) {
                bloc = encryptBloc(bloc);
                System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);
            }
            if (i < in.length)
                bloc[i % 16] = in[i];
            else {
                bloc[i % 16] = padding[count % 16];
                count++;
            }
        }
        if (bloc.length == 16) {
            bloc = encryptBloc(bloc);
            System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);
        }

        return tmp;
    }

    public static byte[] decrypt(byte[] in, byte[] key) {
        int i;
        byte[] tmp = new byte[in.length];
        byte[] bloc = new byte[16];


        Nb = 4;
        Nk = key.length / 4;
        Nr = Nk + 6;
        w = generateSubkeys(key);


        for (i = 0; i < in.length; i++) {
            if (i > 0 && i % 16 == 0) {
                bloc = decryptBloc(bloc);
                System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);
            }
            if (i < in.length)
                bloc[i % 16] = in[i];
        }
        bloc = decryptBloc(bloc);
        System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);


        tmp = deletePadding(tmp);

        return tmp;
    }

    private static byte[] deletePadding(byte[] input) {
        int count = 0;

        int i = input.length - 1;
        while (input[i] == 0) {
            count++;
            i--;
        }

        byte[] tmp = new byte[input.length - count - 1];
        System.arraycopy(input, 0, tmp, 0, tmp.length);
        return tmp;
    }

    public static byte[] encrypt(byte[] in, byte[] key, int n) {

        Nb = 4;
        Nk = key.length / 4;
        Nr = n;

        int lenght = 0;
        byte[] padding = new byte[1];
        int i;
        lenght = 16 - in.length % 16;
        padding = new byte[lenght];
        padding[0] = (byte) 0x80;

        for (i = 1; i < lenght; i++)
            padding[i] = 0;

        byte[] tmp = new byte[in.length + lenght];
        byte[] bloc = new byte[16];


        w = generateSubkeys(key);

        int count = 0;

        for (i = 0; i < in.length + lenght; i++) {
            if (i > 0 && i % 16 == 0) {
                bloc = encryptBloc(bloc);
                System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);
            }
            if (i < in.length)
                bloc[i % 16] = in[i];
            else {
                bloc[i % 16] = padding[count % 16];
                count++;
            }
        }


        if (bloc.length == 16) {
            bloc = encryptBloc(bloc);
            System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);
        }
        return tmp;
    }

    public static byte[] decrypt(byte[] in, byte[] key, int n) {

        int i;
        byte[] tmp = new byte[in.length];
        byte[] bloc = new byte[16];


        Nb = 4;
        Nk = key.length / 4;
        Nr = n;
        w = generateSubkeys(key);


        for (i = 0; i < in.length; i++) {
            if (i > 0 && i % 16 == 0) {
                bloc = decryptBloc(bloc);
                System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);
            }
            if (i < in.length)
                bloc[i % 16] = in[i];
        }
        bloc = decryptBloc(bloc);
        System.arraycopy(bloc, 0, tmp, i - 16, bloc.length);


        tmp = deletePadding(tmp);
        return tmp;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException {


        // double t;
        byte[] k = new byte[16];
        try {
            k = keygeneration();
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
        try {

            File bmpFile = new File("C:\\Users\\acer\\Desktop\\py\\6.bmp");
            BufferedImage image = ImageIO.read(bmpFile);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();//length=32 bytes, though its size increases if necessary.
            ImageIO.write(image, "bmp", baos);
            byte[] b = baos.toByteArray();
            byte[] b2 = new byte[b.length - 620];
            byte[] b1 = new byte[0];

            for (int i = 0; i < (b2.length); i++)
                b2[i] = b[i + 620];
            b2 = encrypt(b2, k, 10);
            b1 = new byte[b2.length + 620];
            for (int i = 0; i < b1.length; i++) {
                if (i < 620) b1[i] = b[i];
                else b1[i] = b2[i - 620];
            }
            bmpFile = new File("C:\\Users\\acer\\Desktop\\py\\en.bmp");
            FileOutputStream fos = new FileOutputStream(bmpFile);
            fos.write(b1);
            fos.flush();
            fos.close();
            for (int i = 0; i < b2.length; i++)
                b2[i] = b1[i + 620];
            b2 = decrypt(b2, k, 10);

            for (int i = 0; i < b.length; i++) {
                if (i < 620) b[i] = b1[i];
                else b[i] = b2[i - 620];
            }
            bmpFile = new File("C:\\Users\\acer\\Desktop\\py\\de.bmp");
            fos = new FileOutputStream(bmpFile);
            fos.write(b);
            fos.flush();
            fos.close();

        } catch (IOException e) {
            System.out.println(e.getMessage());

        }

    }

}

I don't know what is wrong in the code it was supposed to decrypt the image any time.