Add New WordPress Image Sizes

functions.php

<?php

// See https://developer.wordpress.org/reference/functions/add_image_size/ for reference. 
// Also https://bloggerpilot.com/en/disable-wordpress-image-sizes/ 
// Note: You must regenerate thumbnails for new image sizes to be generated. Use Rengenerate Thumbnails plugin.

// Copy the code below into a new snippet using Code Snippets plugin

// Add all new image sizes for the site here, examples:

add_image_size( 'grid-rectangle', 640, 420, true );
add_image_size( 'logo-rectangle', 400, 250, true ); 

// This adds the images sizes above to WordPress interfaces so you can choose them:

add_filter( 'image_size_names_choose', 'my_custom_sizes' );
  
function my_custom_sizes( $sizes ) {
    return array_merge( $sizes, array(
        'grid-rectangle' => __( 'Grid Rectangle' ),
        'logo-rectangle' => __( 'Logo Rectangle' ),
    ) );
}