def getCentralRect(width, height, divisor=1):
    """Select central rectangle with reduced size.

    MMstudio-like.
       1: 2048 1536 (  0,   0, 2048, 1536)
       2: 1024  768 (512, 384, 1536, 1152)
       4:  512  384 (768, 576, 1280, 960)
       8:  256  192 (896, 672, 1152, 864)
      16:  128   96 (960, 720, 1088, 816)
      32:   64   48 (992, 744, 1056, 792)
      64:   32   24 (1008, 756, 1040, 780)
     128:   16   12 (1016, 762, 1032, 774)
     256:    8    6 (1020, 765, 1028, 771)
     512:    4    2 (1022, 767, 1026, 769)
    1024:    2    0 (1023, 768, 1025, 768)

    LeicaDFC 295 available resolutions
    2048 1536
    1600 1200
    1280 1024
    1024  768
     640  480
    """
    centerx = width / 2
    centery = height / 2
    roi = (
        centerx - centerx / divisor,
        centery - centery / divisor,
        width / divisor,
        height / divisor)
    return roi