Must avoid regions outside image boundaries

[academic]

Applying a mask I avoid the pixels on the boundary in case the entire image
is being filtered, so as not to access areas outside the image.

I'd like to do a better job - for example it the Roi does not include an
image boundary I should not avoid that boundary of the Roi.

I been thinking about it and it seems kind of involved.

Not hard to do but many cases to consider and much code

Before I do that I wonder if there is a built-in way to simplify the code.


Thanks in advance for any helpful suggestions