Update and force image sizes in WordPress

image-sizes.php

<?php

add_action( 'switch_theme', function ()
{
    update_option('thumbnail_size_w', 500);
    update_option('thumbnail_size_h', 500);
    update_option('thumbnail_size_cropt', 0);

    update_option('medium_size_w', 1000);
    update_option('medium_size_h', 1000);
    update_option('medium_size_cropt', 0);

    update_option('large_size_w', 2000);
    update_option('large_size_h', 2000);
    update_option('large_size_cropt', 0);
}

add_filter( 'pre_update_option_thumbnail_size_w', 'themename_filter_thumbnail_size_w' );
function themename_filter_thumbnail_size_w( $newvalue ) {
	return 500;
}
           
add_filter( 'pre_update_option_thumbnail_size_h', 'themename_filter_thumbnail_size_h' );
function themename_filter_thumbnail_size_h( $newvalue ) {
	return 500;
}

add_filter( 'pre_update_option_thumbnail_crop', 'themename_filter_thumbnail_crop' );
function themename_filter_thumbnail_crop( $newvalue ) {
	return 0;
}

add_filter( 'pre_update_option_medium_size_w', 'themename_filter_medium_size_w' );
function themename_filter_medium_size_w( $newvalue ) {
	return 1000;
}

add_filter( 'pre_update_option_medium_size_h', 'themename_filter_medium_size_h' );
function themename_filter_medium_size_h( $newvalue ) {
	return 1000;
}

add_filter( 'pre_update_option_large_size_w', 'themename_filter_large_size_w' );
function themename_filter_large_size_w( $newvalue ) {
	return 1500;
}

add_filter( 'pre_update_option_large_size_h', 'themename_filter_large_size_h' );
function themename_filter_large_size_h( $newvalue ) {
	return 1500;
}