EncodeDecode.java

//Encode
private byte[] encode_text(byte[] image, byte[] addition, int offset)
        {
                //check that the data + offset will fit in the image
                if(addition.length + offset > image.length)
                {
                        throw new IllegalArgumentException("File not long enough!");
                }
                //loop through each addition byte
                for(int i=0; i<addition.length; ++i)
                {
                        //loop through the 8 bits of each byte
                        int add = addition[i];
                        for(int bit=7; bit>=0; --bit, ++offset) //ensure the new offset value carries on through both loops
                        {
                                //assign an integer to b, shifted by bit spaces AND 1
                                //a single bit of the current byte
                                int b = (add >>> bit) & 1;
                                //assign the bit by taking: [(previous byte value) AND 0xfe] OR bit to add
                                //changes the last bit of the byte in the image to be the bit of addition
                                image[offset] = (byte)((image[offset] & 0xFE) | b );
                        }
                }
                return image;
        }
//Decode
private byte[] decode_text(byte[] image)
        {
                int length = 0;
                int offset  = 32;
                //loop through 32 bytes of data to determine text length
                for(int i=0; i<32; ++i) //i=24 will also work, as only the 4th byte contains real data
                {
                        length = (length << 1) | (image[i] & 1);
                }
                
                byte[] result = new byte[length];
                
                //loop through each byte of text
                for(int b=0; b<result.length; ++b )
                {
                        //loop through each bit within a byte of text
                        for(int i=0; i<8; ++i, ++offset)
                        {
                                //assign bit: [(new byte value) << 1] OR [(text byte) AND 1]
                                result[b] = (byte)((result[b] << 1) | (image[offset] & 1));
                        }
                }
                return result;
        }