Replace the Youtube embed with a thumbnail

oembed-youtube-thumbnails.php

<?php
	add_filter( 'oembed_result', 'fwe_oembed_result', 10, 3 );
	function fwe_oembed_result( $result, $url, $args ){
		//Uebernommen aus wp-includes/class-oembed.php
		//L38ff
		$youtube_regex = array(
			'#http://((m|www)\.)?youtube\.com/watch.*#i',
			'#https://((m|www)\.)?youtube\.com/watch.*#i',
			'#http://youtu\.be/.*#i',
			'#https://youtu\.be/.*#i',
		);

		$is_youtube = false;
		foreach( $youtube_regex as $regex ){
			if( preg_match( $regex, $url ) && ! $is_youtube ){
				$is_youtube = true;
				break;
			}
		}

		//Wenn es kein Youtube-Link ist
		if( ! $is_youtube )
			return $result;

		//RegEx fuer Youtube ID
		//Quelle: http://stackoverflow.com/questions/2936467/parse-youtube-video-id-using-preg-match
		$youtubeid_regex = '%(?:youtube(?:-nocookie)?\.com/(?:[^/]+/.+/|(?:v|e(?:mbed)?)/|.*[?&]v=)|youtu\.be/)([^"&?/ ]{11})%i';
		if (! preg_match( $youtubeid_regex, $url, $match ) )
			return $result;

		$src = 'https://i.ytimg.com/vi/' . $match[1] . '/hqdefault.jpg';
		$html = '<div class="youtube-wrapper" data-youtube="' .  $match[1] . '"><img src="' . $src . '" alt="Youtube Thumbnail" /></div>';
		return $html;
	}
	
	add_action( 'init', 'init_script' );
	function init_script(){
		wp_enqueue_script( 'youtube-thumbs', plugins_url( '/script.js', __FILE__ ), array( 'jquery' ) );
	}
?>