- Only need 4 (not 5) samples
- Document some of the math
- Use round of CTM to better match 'brute-force' version
Change-Id: Ibcc8e8eabc10158da8eecaba303385ed79218126
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/379847
Reviewed-by: Mike Klein <mtklein@google.com>