x divided by 64px == 2.625 which is rounded up to 3.
      So, each image should be 168px divided by 3 == 56px
      wide. That means that the top and bottom
      bicolor (yellow and purple) images should be 56px wide.
      144px divided by 64px == 2.25 which is rounded down to 2.
      So, each image should be 144px divided by 2 == 72px
      tall. That means that the left and right
      bicolor (orange and blue) images should be 72px tall.
      So, in this third-subtest, the 2 top and bottom sides
   