HTML生成者the_post_thumbnail() &；get_the_post_thumbnail() 可以使用post_thumbnail_html 滤器即使没有后期缩略图，也可以这样做。示例：

/**
 * Filters the post thumbnail HTML.
 *
 * @since 2.9.0
 *
 * @param string       $html              The post thumbnail HTML.
 * @param int          $post_id           The post ID.
 * @param string       $post_thumbnail_id The post thumbnail ID.
 * @param string|array $size              The post thumbnail size. Image size or array of width and height
 *                                        values (in that order). Default \'post-thumbnail\'.
 * @param string       $attr              Query string of attributes.
 */
function wpse_post_thumbnail_html( $html, $post_id, $post_thumbnail_id, $size, $attr ) {
    // Optionally add any logic here for determining what markup to output.
    // $html will be an empty string if there is no post thumbnail.
    $new_html = \'<img src="https://placekitten.com/g/600/600" alt="kitten">\';
    return $new_html;
}
add_action( \'post_thumbnail_html\', \'wpse_post_thumbnail_html\', 10, 5 );

上述解决方案要求主题调用the_post_thumbnail(), 但是，当帖子没有与之关联的缩略图时，它将起作用。

请注意，如果帖子没有缩略图，则上述解决方案在下面的示例中不起作用。这里，条件语句阻止has_post_thumbnail() 从被调用：

// the_post_thumbnail() will only be called if the post has a thumbnail.
if ( has_post_thumbnail() ) {
    the_post_thumbnail( \'large\' );
}

替代技术（改变现有特征图像的src值）wp_get_attachment_image_src 过滤器允许src 要修改的附件的。

此功能强大的过滤器会影响所有附件映像src值，因此有必要添加/删除附加到的回调函数wp_get_attachment_image_src 基于所需条件。

这个begin_fetch_post_thumbnail_html 和end_fetch_post_thumbnail_html 为此，行动是完美的。

下面是一些基于帖子id更改特征图像的示例代码。您可以修改此代码以使用任何必要的逻辑来确定wpse_wp_get_attachment_image_src 应添加和删除回调。

/**
 * Fires before fetching the post thumbnail HTML.
 *
 * Provides "just in time" filtering of all filters in wp_get_attachment_image().
 *
 * @since 2.9.0
 *
 * @param int          $post_id           The post ID.
 * @param string       $post_thumbnail_id The post thumbnail ID.
 * @param string|array $size              The post thumbnail size. Image size or array of width
 *                                        and height values (in that order). Default \'post-thumbnail\'.
 */
function wpse_begin_fetch_post_thumbnail_html( $post_id, $post_thumbnail_id, $size ) {
    // For example, if the post id is 1479, we will add our callback to modify the image.
    // You could use whatever logic you need to determine if the filter should be added.
    if ( 1479 === $post_id ) {
        add_filter( \'wp_get_attachment_image_src\', \'wpse_wp_get_attachment_image_src\', 10, 4 );
    }
} 
add_action( \'begin_fetch_post_thumbnail_html\', \'wpse_begin_fetch_post_thumbnail_html\', 10, 3 );

/**
 * Fires after fetching the post thumbnail HTML.
 *
 * @since 2.9.0
 *
 * @param int          $post_id           The post ID.
 * @param string       $post_thumbnail_id The post thumbnail ID.
 * @param string|array $size              The post thumbnail size. Image size or array of width
 *                                        and height values (in that order). Default \'post-thumbnail\'.
 */
function wpse_end_fetch_post_thumbnail_html( $post_id, $post_thumbnail_id, $size ) {
    // Now we remove the callback so that it only affects the desired post.
    if ( 1479 === $post_id ) {
        remove_filter( \'wp_get_attachment_image_src\', \'wpse_wp_get_attachment_image_src\', 10, 4 );
    }
} 
add_action( \'end_fetch_post_thumbnail_html\', \'wpse_end_fetch_post_thumbnail_html\', 10, 3 ); 

/**
 * Filters the image src result.
 *
 *
 * @param array|false  $image         Either array with src, width & height, icon src, or false.
 * @param int          $attachment_id Image attachment ID.
 * @param string|array $size          Size of image. Image size or array of width and height values
 *                                    (in that order). Default \'thumbnail\'.
 * @param bool         $icon          Whether the image should be treated as an icon. Default false.
 */
function wpse_wp_get_attachment_image_src( $image, $attachment_id, $size, $icon ) {
    $image[0] = \'https://placekitten.com/g/600/600\';
    return $image;
}