I am confused as to what this book's description is saying exactly:
As with discrete convolution, we can put bounds on the sum if we know the filter’s radius, $r$, eliminating all points where the difference between $x$ and $i$ is at least $r$:
The error comes from this sum
They say that points at $x-r$ being integer are discarded from the sum, of which they are not if the ceiling takes them in. This must be an error and it has been confusing me for so long now.