You can call add_image_size()
again to update the existing image size. Assuming it is called medium_large
(Events Manager Pro is a paid plugin so not very much people have it) you can do something like:
<?php
function update_medium_large_size_wpse216595() {
add_image_size( 'medium_large', 600, 255, array( 'center', 'top' ) );
}
add_action( 'init', 'update_medium_large_size_wpse216595', 11 );
Then you will need to regenerate the thumbnails. Although I am not 100% sure that init
is the right hook for the job.
p.s. You can check this if you are using a child theme.
p.s. 2. I am not sure that I understand the center cropping correctly. You many need to play with it a bit. array( 'center', 'top' )
will crop the picture in the center (‘trimming’ the right and left part).