That's a great question! My original plan that once I had extracted all the items from the plate, the app would then detect the average colour of the remaining regions and "fill" the gaps - that wouldn't work well with plates that have different patterns, but would probably be good enough for plates of a single colour.

Due to time constraints (and ultimately solving the majority of the problems I had originally aimed to with this project), the app replaces the cropped circular region with a plain white plate (a separate image contained in the app) before placing the extracted items.

Maybe I'll go for the more advanced implementation if/when I spend more time on this project!