automatic splitting of a single picture, containing many cards, into separate pictures

Dear all,

I have thousands of scans containing multiple cards per scan. See below for an example. I am looking for a way to automatically split these scans into individual cards. I can't get the automatic crop and straightening-function in Photoshop to work: not all of the cards are split. But as I am no expert in Photoshop, that doesn't mean that it can't be done. Any ideas?

Thanks in advance, Elmer