1、开启缩略图
/*
* Enable support for Post Thumbnails on posts and pages.
*
* @link https://developer.wordpress.org/themes/functionality/featured-images-post-thumbnails/
*/
add_theme_support( 'post-thumbnails' );
2、设置post thumbnail size,
// Set post thumbnail size.
set_post_thumbnail_size( 1200, 9999 );
3、添加自定义 封面的 图像尺寸
// Add custom image size used in Cover Template.
add_image_size( 'twentytwenty-fullscreen', 1980, 9999 );
说明: