NSTableView row mask

NSTableView row mask

I have a 69x69 UIImage in a table view row that is 69 high. I want the
UIImage to abut the top, left, and bottom of the row, but can't quite
figure it out since in each section of the table the first and last rows
have rounded corners. If I put the image right up against the edge, it
looks fine in the middle rows, but it goes over the rounded edge of the
first and last rows. Is there a simple setting in Storyboard to use the
table cell as a mask over the UIImage or as a boundary for the UIImage? Or
do I have to programmatically mask the UIImage depending on which cell it
is in?
Thanks!