You need to register the image size first using add_image_size()
, for example:
add_action( 'after_setup_theme', 'cyb_add_image_sizes' );
function cyb_add_image_sizes() {
add_image_size( 'my-image-size-name', 120, 120, true );
}
Then, you can use the image_size_names_choose
filter (you have misspelled it with image_size_names_chooser
):
add_filter( 'image_size_names_choose', 'rudr_new_image_sizes' );
function rudr_new_image_sizes( $sizes ) {
$addsizes = array(
"my-image-size-name" => 'Misha size'
);
$newsizes = array_merge( $sizes, $addsizes );
return $newsizes;
}