Formal way of saying "dig it out"

I am writing an academic manuscript to describe the action of "digging certain stuff out." For instance, given an image containing several pedestrians, my image analysis techniques can extract those pedestrians as separate small images.

While "digging pedestrians out of the background image" seems legit, it sounds a bit too verbal to me. Therefore, I am writing to inquire some comments on a "formal" way of saying "digging certain stuff out" in my context. Thanks a lot.

Depending on exactly what you mean by "digging them out" I would have thought that either "extracting" if the image data is useful or "removing/deleting" if the data is discarded would be appropriate. I would say "extracting/deleting pedestrians' images out of the background" though, to clarify the exact goal of the exercise.