I want to take partial screen shots for a program I am building. Anyone know where I can look to do this?

I am trying to take a small screen shot. Is there a way to do this?

I have code that captures a window and displays a cropped image. The problem is 2 fold. Kit doesn't seem to allow to modify stop and recapture image in window mode to capture a portion of the screen. So this makes me having to crop and display the cropped image via a published variable. This all works find. But seems to stop after some time. Using an M1 16gig ram. program is taking less than 100meg of mem with 40-70%cpu as the crow flies. printing captured success in debug mode and sometimes frame isn't valid so guarding against it. any ideas on how to improve my strategy?