class LazyLoad_Images {

const version = '0.3';

function init() {
add_action( 'wp_enqueue_scripts', array( __CLASS__, 'add_scripts' ) );
add_filter( 'the_content', array( __CLASS__, 'add_image_placeholders' ), 11 );
add_filter( 'post_thumbnail_html', array( __CLASS__, 'add_image_placeholders' ), 11 );
}

function add_scripts() {
wp_enqueue_script( 'wpcom-lazy-load-images', self::get_url( 'js/lazy-load.js' ), array( 'jquery', 'jquery-sonar' ), self::version, true );
wp_enqueue_script( 'jquery-sonar', self::get_url( 'js/jquery.sonar.min.js' ), array( 'jquery' ), self::version, true );
}

function add_image_placeholders( $content ) {
// Don't lazyload for feeds, previews, mobile
if( is_feed() || is_preview() || ( function_exists( 'is_mobile' ) && is_mobile() ) )
return $content;

// In case you want to change the placeholder image
$placeholder_image = apply_filters( 'lazyload_images_placeholder_image', self::get_url( 'images/1x1.trans.gif' ) );

// This is a pretty simple regex, but it works
$content = preg_replace( '#]+?)src=[\'"]([^\'">]*)[\'"]([^>]*)>#', sprintf( '', $placeholder_image ), $content );

return $content;
}

function get_url( $path = '' ) {
return plugins_url( ltrim( $path, '/' ), __FILE__ );
}
}