Pulls Resized Images From Customizer Settings in WordPress

customizer-custom-image-sizes.php

<?php
if ( ! class_exists( 'My_Customizer_Theme_Mods' ) ) {
	class My_Customizer_Theme {
		var $version = '0.1';
		
		function __construct() {
		  /**
		   * We have two basic sizes of images used from the images set in the Customizer
		   *    One of them is full-width of the browser, so let's make it large, but not unlimited
		   *    The other is a 125x125 icon, but, just in case it needs to be a bit larger on mobile or 
		   *      something, we'll set it a bit larger than that
		   */
			add_image_size( 'parallax_background', 2560, 1920, false );
			add_image_size( 'home_box_icon', 300, 225, false );
			
			/**
			 * Let's gather a list of the Customizer areas that get output as 125x125 icons
			 */
			$this->icon_mods = array( 'featured_box1_image', 'featured_box2_image', 'featured_box3_image' );
			foreach ( $this->icon_mods as $name ) {
				add_filter( "theme_mod_{$name}", array( $this, 'get_resized_theme_mod_icon' ) );
			}
			
			/**
			 * Let's gather a list of the Customizer areas that get output as full-width backgrounds
			 */
			$this->bg_mods = array( 'subheader_bgimg', 'home_footer_bgimg' );
			foreach ( $this->bg_mods as $name ) {
				add_filter( "theme_mod_{$name}", array( $this, 'get_resized_theme_mod_image' ) );
			}
		}
		
		/**
		 * Tries to convert an attachment URL into a post ID.
		 * This version of this function was copied almost directly from the 
		 *    code within WordPress Core; it's just a backup in case the 
		 *    function doesn't exist within Core for some reason
		 *
		 * @since 4.0.0
		 *
		 * @global wpdb $wpdb WordPress database abstraction object.
		 *
		 * @param string $url The URL to resolve.
		 * @return int The found post ID, or 0 on failure.
		 */
		function attachment_url_to_postid( $url ) {
			/**
			 * Default to the one included with WP; if that doesn't 
			 *  	exist for some reason, we'll use the one copped from WP 4.3+
			 */
			if ( function_exists( 'attachment_url_to_postid' ) ) {
				return attachment_url_to_postid( $url );
			}
			
			/**
			 * Proceed with the one we copied from Core if the function 
			 *    didn't exist in Core for some reason
			 */
			global $wpdb;
		
			$dir = wp_upload_dir();
			$path = $url;
		
			$site_url = parse_url( $dir['url'] );
			$image_path = parse_url( $path );
		
			//force the protocols to match if needed
			if ( isset( $image_path['scheme'] ) && ( $image_path['scheme'] !== $site_url['scheme'] ) ) {
				$path = str_replace( $image_path['scheme'], $site_url['scheme'], $path );
			}
		
			if ( 0 === strpos( $path, $dir['baseurl'] . '/' ) ) {
				$path = substr( $path, strlen( $dir['baseurl'] . '/' ) );
			}
		
			$sql = $wpdb->prepare(
				"SELECT post_id FROM $wpdb->postmeta WHERE meta_key = '_wp_attached_file' AND meta_value = %s",
				$path
			);
			$post_id = $wpdb->get_var( $sql );
		
			/**
			 * Filter an attachment id found by URL.
			 *
			 * @since 4.2.0
			 *
			 * @param int|null $post_id The post_id (if any) found by the function.
			 * @param string   $url     The URL being looked up.
			 */
			return (int) apply_filters( 'attachment_url_to_postid', $post_id, $url );
		}
		
		/**
		 * Get the URL of a specifically-sized image to be used in a Customizer-set location
		 *
		 * @param string $img the image URL that's stored in the Customizer settings
		 * @param string|array $size='parallax_background' the predefined image size to return
		 * @return string the URL to the appropriately-sized image (or the original URL if the size was not found)
		 */
		function get_resized_theme_mod_image( $img, $size='parallax_background' ) {
		  /**
		   * If we're in the admin area (or in the Customizer), skip this process
		   */
			if ( is_admin() )
				return $img;
			
			/**
			 * Attempt to get the ID of the image attachment
			 */
			$id = $this->attachment_url_to_postid( $img );
			if ( empty( $id ) || is_wp_error( $id ) || ! is_numeric( $id ) ) {
				return $img;
			}
			
			/**
			 * Get the URL to the appropriately-sized image
			 */
			$img = wp_get_attachment_image_src( $id, $size );
			if ( is_array( $img ) && esc_url( $img[0] ) ) {
				return esc_url( $img[0] );
			}
			
			return $img;
		}
		
		/**
		 * This is an alias of the My_Customizer_Theme::get_resized_theme_mod_image() method that
		 *    requests the 'home_box_icon' image size instead of the 'parallax_background' size
		 */
		function get_resized_theme_mod_icon( $img ) {
			return $this->get_resized_theme_mod_image( $img, 'home_box_icon' );
		}
	}
}