Crop image to horizontal or vertical by code based on image size

my client asked me to create gallery(WP gallery) based on this site.

the problem here is that i need to crop images based on image size before inserting the image in the Media library.

now i using this code to check the image width and height:

add_filter('wp_handle_upload_prefilter','validate_image_size');
function validate_image_size( $file ) {

$image = getimagesize($file['tmp_name']);
$image_width = $image[0];
$image_height = $image[1];

if ($image_width > $image_height) {
// crop to horizontal
}

if ($image_height > $image_width) {
// crop to vertical
}
}

1. how can i crop image to horizontal or vertical?

2. how can i show all images after crop based on the order of this site: site

always 2 vertical images in line or horizontal on line?

why didn’t use add_image_size( 'horizontal_img', 800, 300, true ); add_image_size( 'vertical_img', 300, 800, true );

And then
$image_hor = wp_get_attachment_image_src($post_id,'horizontal_img');
$image_ver = wp_get_attachment_image_src($post_id,'vertical_img');

when
echo $image_hor[0] you will get your desire sized image url.

Thanks
Musa