Let’s keep it simple. Divi filterable portfolio by default outputs at a ratio of 400x284 to your featured images. I wanted squares images. If that’s your goal, then here’s your solution. Just add the following code to your functions.php. If you want your dimensions larger, then just change anywhere where it says 250. Simple.

// Begin custom image size for Portfolio Thumbs
add_filter( 'et_pb_portfolio_image_height', 'port_size_h' );
add_filter( 'et_pb_portfolio_image_width', 'port_size_w' );

function port_size_h($height) {
return '1000';
}
change-divi-image-portfolio-grid-thumbnail-sizes
function port_size_w($width) {
return '1000';
}

add_image_size( 'custom-port-size', 1000, 1000 );
// End custom image size for Portfolio Thumbs