When I put a light-colored ID card on the table that is also light-colored Or anything with a light background , he cannot detect the corners Or a dark card on a dark background also cannot detect , To clarify, the card is light blue and the table is white, slightly gray and he can't detect corners.
case 2 :
When holding the card with two fingers and trying to make corner detect, it also doesn't detect Regardless of the color of the card.
case 1 :
case 2 :