From looking at the output and the code, it seems to skip (1/6th) of the rows and columns, this adds up to about 30% fewer pixel operations.
Dropping the comparisons by only 30% seems like a poor savings, especially since it makes the diff quite a bit less useful:
From looking at the output and the code, it seems to skip (1/6th) of the rows and columns, this adds up to about 30% fewer pixel operations.
Dropping the comparisons by only 30% seems like a poor savings, especially since it makes the diff quite a bit less useful:
