Check for featured image in WP_Query

Question

Is there a way to filter posts by featured image when initialising a WP_Query object?

Example

$my_query = WP_Query(array("has_thumbnail"=>true));

or, more ideally

$my_query = WP_Query(array("has_thumbnail_size"=>"custom_size"));

Answer 1

Technically featured image is custom field with name _thumbnail_id that holds attachment ID. So you can easily query with something like:

$args = array(
    'meta_query' => array(
        array(
            'key' => '_thumbnail_id',
        )
    )
 );
$query = new WP_Query( $args );

Size on other hand is attribute of that attachment and not post itself. You will need to loop through attachment and get sizes they have (if I remember right it should be in data returned by wp_get_attachment_metadata()).

Answer 2

Here's an alternate approach of filtering the posts after the query using whether the wp_get_attachment_thumb_url() returns an empty string to determine if the post has a thumbnail (featured image).

//get all the posts however your query does it. simple example when there aren't a lot: 
$args = array("nopaging" => true);
$posts = (new WP_Query($args))->posts;

//filter the posts array by looking up the thumb_url and seeing if it's empty
$posts_without_thumbnails = array_filter($posts,  function($post){
  $post_thumbnail_id = get_post_thumbnail_id( $post->ID );
  return ( wp_get_attachment_thumb_url( $post_thumbnail_id ) == "");
} );

If you need this to happen during the query, you can probably make a wordpress filter or action out of it or intercept the query_posts.