Favicon generator

creator.php

<?php

class WP_Site_Icon_Creator {
	private $file;

	public function __construct() {
		$this->file = dirname( __FILE__ ) . '/512px_Icon.png';
		$this->generate();
	}

	public function generate() {
		$editor = wp_get_image_editor( $this->file );

		if ( is_wp_error( $editor ) ) {
			return false;
		}

		$upload_dir = wp_upload_dir();

		$sizes = get_site_icon_sizes();
		uasort( $sizes, array( $this, 'order_by_size' ) );

		foreach ( $sizes as $id => $args ) {
			$editor->resize( $args['size'], $args['size'], true );

			$resized_file = $editor->save( $upload_dir['basedir'] . '/icons/' . $id );
		}

		if ( $editor->supports_mime_type('image/x-icon') ) {
			$editor->resize( 16, 16, true );

			$resized_file = $editor->save( $upload_dir['basedir'] . '/icons/favicon.ico' );
		}

		exit;
	}

	public function order_by_size( $a, $b ) {
		return ( $a['size'] > $b['size'] ) ? -1 : 1;
	}

}

sizes.php

<?php
<?php

class WP_Site_Icon_Sizes {
	protected $sizes = array();

	public function __construct() {
		foreach ( array( 16, 32, 96, 192 ) as $size ) {
			$this->add( "favicon-{$size}", array(
				'label'            => __( 'Favicon %s' ),
				'size'             => $size,
				'scalable'         => true,
				'display_callback' => array( $this, 'display_favicon' ),
			) );
		}

		foreach ( array( 120, 152 ) as $size ) {
			$this->add( "touch-icon-{$size}", array(
				'label'            => __( 'Touch Icon %s' ),
				'size'             => $size,
				'scalable'         => true,
				'display_callback' => array( $this, 'display_touch_icon' ),
			) );
		}
	}

	public function add( $id, array $args ) {
		$this->sizes[ $id ] = $args;
		return true;
	}

	public function remove( $id ) {
		if ( isset( $this->sizes[ $id ] ) ) {
			unset( $this->sizes[ $id ] );
			return true;
		} else {
			return false;
		}
	}

	public function get_all() {
		return $this->sizes;
	}

	public function display_favicon( $size, $src, WP_Post $attachment ) {
		$mime_type = explode( '/', get_post_mime_type( $attachment ) );

		$icon = sprintf( '<link rel="icon" sizes="%1$dx%1$d" href="$2%s" type="image/%3$d">',
			absint( $size ),
			esc_url( $src ),
			esc_attr( $mime_type[1] )
		);
		return $icon;
	}

	public function display_touch_icon( $size, $src, WP_Post $attachment ) {
		$icon1x = sprintf( '<link rel="apple-touch-icon-precomposed" sizes="%1$dx%1$d" href="$2%s">',
			absint( $size ) / 2,
			esc_url( $src )
		);
		$icon2x = sprintf( '<link rel="apple-touch-icon-precomposed" sizes="%1$dx%1$d" href="$2%s">',
			absint( $size ),
			esc_url( $src )
		);
		return $icon1x . $icon2x;
	}

	/**
	 * Singleton.
	 *
	 * @return WP_Site_Icon_Sizes Site Icon Sizes instance.
	 */
	public static function get_instance() {
		static $instance;

		if ( ! isset( $instance ) ) {
			$instance = new WP_Site_Icon_Sizes;
		}

		return $instance;
	}

}