Java - 将 byte[] 转换为 int[] rgb

Question

I have an int array that i obtained by using RobotPeer.getRGBPixels(). I convert it to an byte array to send it over socket by using:

 public static byte[] toByteArray(int[] ints){
    byte[] bytes = new byte[ints.length * 4];
            for (int i = 0; i < ints.length; i++) {
        bytes[i * 4] = (byte) (ints[i] & 0xFF);
        bytes[i * 4 + 1] = (byte) ((ints[i] & 0xFF00) >> 8);
        bytes[i * 4 + 2] = (byte) ((ints[i] & 0xFF0000) >> 16);
        bytes[i * 4 + 3] = (byte) ((ints[i] & 0xFF000000) >> 24);
    }
    return bytes;
}

Problem is: I use this method:

public static int[] toIntArray(byte buf[]) {
    int intArr[] = new int[buf.length / 4];
    int offset = 0;
    for (int i = 0; i < intArr.length; i++) {
        intArr[i] = (buf[3 + offset] & 0xFF) | ((buf[2 + offset] & 0xFF) << 8)
                | ((buf[1 + offset] & 0xFF) << 16) | ((buf[0 + offset] & 0xFF) << 24);
        offset += 4;
    }
    return intArr;
}

to get back int array. Then i create BufferedImage from it and i get: https://www.dropbox.com/s/p754u3tnivigu70/test.jpeg

Please help me to solve that problem.

Answer 1

Don't bother with bit shifting etc; Java has ByteBuffer which can handle that for you, and endianness to boot:

public static int[] toIntArray(byte buf[]) 
{
    final ByteBuffer buffer = ByteBuffer.wrap(buf)
        .order(ByteOrder.LITTLE_ENDIAN);
    final int[] ret = new int[buf.length / 4];
    buffer.asIntBuffer().put(ret);
    return ret;
}

Similarly, the reverse:

public static byte[] toByteArray(int[] ints)
{
    final ByteBuffer buf = ByteBuffer.allocate(ints.length * 4)
        .order(ByteOrder.LITTLE_ENDIAN);
    buf.asIntBuffer().put(ints);
    return buf.array();
}

Don't forget to specify endianness in your case since ByteBuffer s are big endian by default.