[Smush] - Background Images Fix. Add unquoted background image support

wpmudev-smush-background-image-support.php

<?php
/**
* Plugin Name: [Smush] - Background Images Fix
* Plugin URI: https://premium.wpmudev.org/
* Description: Add unquoted background image support
* Author: Alessandro Kaounas & Tho Bui @ WPMUDEV
* Author URI: https://premium.wpmudev.org/
* License: GPLv2 or later
*/

if (! defined('ABSPATH')) {
    exit;
}

add_action('after_setup_theme', 'wpmudev_smpro_fix_background_issue_func', 100);

function wpmudev_smpro_fix_background_issue_func()
{
    if (defined('WP_SMUSH_VERSION') && class_exists('WP_Smush') && class_exists('Smush\Core\Settings')) {
        if (! class_exists('WPMUDEV_Smush_Background_Images_Fix')) {
            
            class WPMUDEV_Smush_Background_Images_Fix
            {

                private static $_instance       = null;
                private $background_images      = false;
                protected $settings             = null;

                public static function get_instance()
                {

                    if (is_null(self::$_instance)) {
                        self::$_instance = new WPMUDEV_Smush_Background_Images_Fix();
                    }
                    return self::$_instance;
                }

                private function __construct()
                {

                    $this->init();
                }

                private function init()
                {
                    
                    if (! class_exists('WP_Smush')) {
                        return;
                    }

                    add_action('template_redirect', array( $this, 'attempt_alter_buffer' ));

                    $this->settings = Smush\Core\Settings::get_instance();
                    $this->background_images = intval($this->settings->get('background_images'));
                }

                public function attempt_alter_buffer()
                {
                    
                    ob_start(array( $this, 'maybe_alter_buffer' ));
                }

                public function maybe_alter_buffer($content, $flags)
                {

                    $content = ob_get_contents();

                    if ($this->background_images) {
                        $content = $this->process_background_images($content);
                    }

                    return $content;
                }

                private function process_background_images($content)
                {
                    
                    $images = self::get_background_images($content);

                    if (empty($images)) {
                        return $content;
                    }

                    foreach ($images[0] as $key => $image) {
                        $img_src = $images['img_url'][ $key ];

                        // Update the image with correct CDN links.
                        $new_image = WP_Smush::get_instance()->core()->mod->cdn->generate_cdn_url($img_src);
                        
                        $content = str_replace($img_src, $new_image, $content);
                    }

                    return $content;
                }


                private static function get_background_images($content)
                {
                    
                    $images = array();

                    if (preg_match_all('/(?:background(-image)?:[^:;]*?url\([\'|"]?(?P<img_url>http?s?:?\/\/[^"\']*\.(?:png|jpg|jpeg|gif))[\'|"]?\)?;){1}/is', $content, $images)) {
                        foreach ($images as $key => $unused) {
                            // Simplify the output as much as possible, mostly for confirming test results.
                            if (is_numeric($key) && $key > 0) {
                                unset($images[ $key ]);
                            }
                        }
                    }

                    return $images;
                }
            }

            $run = WPMUDEV_Smush_Background_Images_Fix::get_instance();
        }
    }
}