Crops selected by Select box in repeater fields

I created a Bento Box grid. The size and orientation (portrait, landscape, square) is controlled by a dropdown field. And I have an image field with corresponding crops.
I can use the placeholder i.e. [[+crops.portrait.url]] inside the image field, but how to change it by the dropdown?

Assuming the orientation is in [[+orientation]] which matches the name of a crop, perhaps you can use something like this?