By adjusting the internal scaling and rounding in the transforms,
we can adjust the maximum round-trip errors to:
* 8x16 and 16x8: 0 pixel values (ie, transforms are exact)
* 16x32: 1 pixel value
* 32x16: 2 pixel values

Change-Id: I0ba691a8d27042dcf1dd5ae81568d07a92d68781