How to efficiently change endianess of byte array in Java

Question

I have a long array of bytes which represents abgr32 pixel data (0xAABBGGRR) of a big picture. Is there an efficient way to change the endiness of this long byte array in java?

For example:

Source byte array is [FF,11,22,33,FF,12,34,11,..........]

Is it possible to convert it to something like this [33,22,11,FF,11,34,12,FF,....] ? Efficiency is important.

I have tryed to use ByteBuffer.order(ByteOrder.LITTLE_ENDIAN) and ByteBuffer.order(ByteOrder.BIG_ENDIAN) conversion but it didn't help.

Thank you for your help.

Answer 1

You can try doing it manually by swapping the bytes in each group of adjacent 4 bytes. This code assumes that the length of the array is a multiple of 4.

for (int i = 0; i < arr.length; i += 4) {
  int tmp;
  // swap 0 and 3
  tmp = arr[i];
  arr[i] = arr[i + 3];
  arr[i + 3] = tmp;
  // swap 1 and 2
  tmp = arr[i + 1];
  arr[i + 1] = arr[i + 2];
  arr[i + 2] = tmp;
}

Though this is technically a solution to the problem, it may be wiser to find a solution which is not endian-ness sensitive (like some of the comments above).