NV21数据的镜像算法

//NV21: YYYY VUVU
byte[] NV21_mirror(byte[] nv21_data, int width, int height)
{
  int i;
  int left, right;
  byte temp;
  int startPos = 0;
  // mirror Y
  for (i = 0; i < height; i++)
  {
    left  = startPos;
    right = startPos + width - 1;
    while (left < right)
    {
      temp             = nv21_data[left];
      nv21_data[left]  = nv21_data[right];
      nv21_data[right] = temp;
      left ++;
      right--;
    }
    startPos += width;
  }
  // mirror U and V
  int offset = width * height;
  startPos = 0;
  for (i = 0; i < height / 2; i++)
  {
    left  = offset + startPos;
    right = offset + startPos + width - 2;
    while (left < right)
    {
      temp             = nv21_data[left ];
      nv21_data[left ] = nv21_data[right];
      nv21_data[right] = temp;
      left ++;
      right--;
      temp       = nv21_data[left ];
      nv21_data[left ] = nv21_data[right];
      nv21_data[right] = temp;
      left ++;
      right--;
    }
    startPos += width;
  }
  return nv21_data;
}