Extracting multiple photos from a single quickly I recently went through the process of scanning old photo albums (in an effort to preserve them longer digitized). I would place 2/3/4 photos on the scanner. Now I need to extract the single photos. It would also help if there was an application to quickly recognize the rectangles.

N.B.: I'm running the latest beta of Sierra.
You could use ImageMagick or NetPbm tools to crop the photos from a script, but it isn't going to automatically detect the rectangle edges.

Lay out your photos in roughly the same place every time you scan them. Leaving a small gap between the photos would give you a safety buffer; the resulting scanned/cropped photos will just have a white border around them.