以下是我从kg_video_attachment_fields_to_save() 过滤附件\\u字段\\u以保存的函数：

    $thumb_url = $attachment[\'kgflashmediaplayer-poster\'];

    //insert the $thumb_url into the media library if it does not already exist
    if ( ! ($thumb_id = get_attachment_id_from_src( $thumb_url ) ) ) {

        $post_id = $post[\'ID\'];
        $desc = $attachment[\'post_title\'] . \' thumbnail\';

        //is image in uploads directory?
        $upload_dir = wp_upload_dir();

        if ( FALSE !== strpos( $url, $upload_dir[\'baseurl\'] ) ) {
            $wp_filetype = wp_check_filetype(basename($thumb_url), null );
            $filename = preg_replace(\'/\\.[^.]+$/\', \'\', basename($thumb_url));

            $attachment = array(
               \'guid\' => $thumb_url, 
               \'post_mime_type\' => $wp_filetype[\'type\'],
               \'post_title\' => $desc,
               \'post_content\' => \'\',
               \'post_status\' => \'inherit\'
            );
            $thumb_id = wp_insert_attachment( $attachment, basename($thumb_url), $post_id );
            // you must first include the image.php file
            // for the function wp_generate_attachment_metadata() to work
            require_once(ABSPATH . \'wp-admin/includes/image.php\');
            $attach_data = wp_generate_attachment_metadata( $thumb_id, basename($thumb_url) );
            wp_update_attachment_metadata( $thumb_id, $attach_data );
        } else { //not in uploads so we\'ll have to sideload it
            $tmp = download_url( $thumb_url );

            // Set variables for storage
            // fix file filename for query strings
            preg_match(\'/[^\\?]+\\.(jpg|JPG|jpe|JPE|jpeg|JPEG|gif|GIF|png|PNG)/\', $thumb_url, $matches);
            $file_array[\'name\'] = basename($matches[0]);
            $file_array[\'tmp_name\'] = $tmp;

            // If error storing temporarily, unlink
            if ( is_wp_error( $tmp ) ) {
                @unlink($file_array[\'tmp_name\']);
                $file_array[\'tmp_name\'] = \'\';
            }

            // do the validation and storage stuff
            $thumb_id = media_handle_sideload( $file_array, $post_id, $desc );

            // If error storing permanently, unlink
            if ( is_wp_error($thumb_id) ) {
                @unlink($file_array[\'tmp_name\']);
                return $thumb_id;
            }

            if ( $local_src = wp_get_attachment_url( $thumb_id ) ) {
                update_post_meta($post[\'ID\'], \'_kgflashmediaplayer-poster\', $local_src);
            }

        } //end sideload

    } //end get_attachment_id_from_src

    if(!is_wp_error($thumb_id)) {
        $thumb_id = intval( $thumb_id );
        update_post_meta($post[\'ID\'], \'_kgflashmediaplayer-poster-id\', $thumb_id);
    } 

视频的自定义缩略图ID现在存储在元字段中：_kgflashmediaplayer-poster-id

function get_attachment_id_from_src ($image_src) {
    global $wpdb;

    $query = "SELECT ID FROM {$wpdb->posts} WHERE guid=\'$image_src\'";
    $id = $wpdb->get_var($query);
    return $id;

}

我不喜欢get_attachment_id_from_src() 但没有内置的方法来实现这一点。我应该添加一个检查，以便如果当前src与旧源相同，则不需要运行此查询。embedder插件为每个视频创建了许多潜在的缩略图，无需将它们全部插入媒体库。。。。因此，每当保存媒体附件时，就会触发此操作，并应涵盖媒体库中已有的图像、媒体目录中但不在库中的图像以及其他服务器上的图像（这些服务器会被侧加载，并且URL会调整为新的本地URL）