maximum height imagebrowser or singlepic nextgen-gallery

I want my images in the imagebrowser to have a maximum height
(or a maximum width and height)

Right now portrait images are taking to much space and forces the back and next arrows down so you have to scroll to click them.

is there a way to set the portrait images to have a maximum hight to, for example, 375 pixels?

Can i do this in CSS? or somewhere in the PHP?

Help would be very appreciated.

Thank you!