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<?php |
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/** |
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* Plugin Name: Lazy Images |
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* Description: Load images just before they scroll into view |
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* Plugin URI: https://github.com/automattic/jetpack |
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* Author: Automattic |
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* Author URI: https://automattic.com |
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* Version: 0.1.0 |
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* Text Domain: lazy-images |
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* Domain Path: /languages/ |
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* License: GPLv2 or later |
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*/ |
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/** |
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* Props to batmoo for https://wordpress.org/plugins/lazy-load/ |
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* https://profiles.wordpress.org/batmoo |
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*/ |
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class Jetpack_Lazy_Images { |
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private static $__instance = null; |
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/** |
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* Singleton implementation |
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* |
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* @return object |
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*/ |
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public static function instance() { |
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if ( ! is_a( self::$__instance, 'Jetpack_Lazy_Images' ) ) { |
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self::$__instance = new Jetpack_Lazy_Images(); |
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} |
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return self::$__instance; |
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} |
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/** |
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* Registers actions |
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*/ |
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private function __construct() { |
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// modify content |
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add_action( 'wp_head', array( $this, 'setup_filters' ), 9999 ); // we don't really want to modify anything in <head> since it's mostly all metadata |
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// js to do lazy loading |
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add_action( 'init', array( $this, 'register_assets' ) ); |
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add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_assets' ) ); |
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} |
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public function setup_filters() { |
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add_filter( 'the_content', array( $this, 'add_image_placeholders' ), 99 ); // run this later, so other content filters have run, including image_add_wh on WP.com |
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add_filter( 'post_thumbnail_html', array( $this, 'add_image_placeholders' ), 11 ); |
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add_filter( 'get_avatar', array( $this, 'add_image_placeholders' ), 11 ); |
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} |
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public function add_image_placeholders( $content ) { |
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// Don't lazyload for feeds, previews |
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if( is_feed() || is_preview() ) |
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return $content; |
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// Don't lazy-load if the content has already been run through previously |
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if ( false !== strpos( $content, 'data-lazy-src' ) ) |
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return $content; |
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// This is a pretty simple regex, but it works |
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$content = preg_replace_callback( '#<(img)([^>]+?)(>(.*?)</\\1>|[\/]?>)#si', array( __CLASS__, 'process_image' ), $content ); |
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return $content; |
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} |
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function process_image( $matches ) { |
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$old_attributes_str = $matches[2]; |
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$old_attributes = wp_kses_hair( $old_attributes_str, wp_allowed_protocols() ); |
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if ( empty( $old_attributes['src'] ) ) { |
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return $matches[0]; |
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} |
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$image_src = $old_attributes['src']['value']; |
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if ( isset( $old_attributes['srcset'] ) ) { |
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$image_srcset = $old_attributes['srcset']['value']; |
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} else { |
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$image_srcset = ''; |
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} |
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// Remove src, lazy-src, srcset and lazy-srcset since we manually add them |
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$new_attributes = $old_attributes; |
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unset( $new_attributes['src'], $new_attributes['srcset'], $new_attributes['data-lazy-src'], $new_attributes['data-lazy-srcset'] ); |
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$new_attributes_str = $this->build_attributes_string( $new_attributes ); |
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return sprintf( '<img data-lazy-src="%1$s" data-lazy-srcset="%2$s" %3$s><noscript>%4$s</noscript>', esc_url( $image_src ), esc_attr( $image_srcset ), $new_attributes_str, $matches[0] ); |
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} |
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private function build_attributes_string( $attributes ) { |
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$string = array(); |
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foreach ( $attributes as $name => $attribute ) { |
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$value = $attribute['value']; |
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if ( '' === $value ) { |
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$string[] = sprintf( '%s', $name ); |
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} else { |
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$string[] = sprintf( '%s="%s"', $name, esc_attr( $value ) ); |
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} |
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} |
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return implode( ' ', $string ); |
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} |
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public function register_assets() { |
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wp_register_script( 'jetpack-lazy-images', plugins_url( 'assets/js/lazy-images.js', __FILE__ ), array('jquery'), '1.5', true ); |
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wp_register_script( 'jetpack-intersection-observer-polyfill', plugins_url( 'assets/js/intersection-observer.js', __FILE__ ), array('jquery'), '1.5' ); |
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wp_script_add_data( 'jetpack-intersection-observer-polyfill', 'conditional', 'IE' ); |
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} |
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public function enqueue_assets() { |
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wp_enqueue_script( 'jetpack-lazy-images' ); |
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wp_enqueue_script( 'jetpack-intersection-observer-polyfill' ); |
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} |
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} |
Automattic /
jetpack
