Testing seek back after a rejected subimage:
  opened: True
  seek to subimage 1 rejected: True
  seek back to subimage 0 ok: True
  spec is subimage 0's: True
  read_image shape: (1, 1, 1)
  read_image value: 17 (expected 17)

Testing ImageCache read after a rejected subimage:
  get_pixels ok: True
  get_pixels value: 17 (expected 17)

Done.
