Is this a standard deck of cards? If you could put a QR code on the cards you would probably make your job easier. If it is a standard deck then the upper left of the card will have digit/s or a letter plus a symbol defining the card. I am not sure how much the positioning and type faces differ between different decks. I suppose though you only have four symbols in two colours so the image recognition part might be relatively simple.
It still sounds though like something not well suited to an Arduino