这里有一段很实用的代码，可以自动将文章中的第一张图片设置为特色图像，如果你手动设置了特色图像，可以覆盖这段代码。将下面的代码丢到当前主题的functions.php里，以后就不用担心忘记设置特色图像了。

function autoset_featured() {
global $post;
$already_has_thumb = has_post_thumbnail($post->ID);
if (!$already_has_thumb) {
$attached_image = get_children( “post_parent=$post->ID&post_type=attachment&post_mime_type=image&numberposts=1” );
if ($attached_image) {
foreach ($attached_image as $attachment_id => $attachment) {
set_post_thumbnail($post->ID, $attachment_id);
}
}
}
} //end function
add_action(‘the_post’, ‘autoset_featured’);
add_action(‘save_post’, ‘autoset_featured’);
add_action(‘draft_to_publish’, ‘autoset_featured’);
add_action(‘new_to_publish’, ‘autoset_featured’);
add_action(‘pending_to_publish’, ‘autoset_featured’);
add_action(‘future_to_publish’, ‘autoset_featured’);

有的主题上默认不显示特色主题，也就是新增文章的时候没有地方可以选择，可以在主题的functions.php中添加如下代码

//使WordPress支持post thumbnail
if ( function_exists( ‘add_theme_support’ ) ) {
add_theme_support( ‘post-thumbnails’ );
}

https://www.solagirl.net/how-to-setup-featured-image-in-wordpress.html

https://www.solagirl.net/automatically-set-the-featured-image-in-wordpress.html