Source

File: wp-includes/link-template.php

function get_avatar_data( $id_or_email, $args = null ) {
	$args = wp_parse_args(
		$args,
		array(
			'size'           => 96,
			'height'         => null,
			'width'          => null,
			'default'        => get_option( 'avatar_default', 'mystery' ),
			'force_default'  => false,
			'rating'         => get_option( 'avatar_rating' ),
			'scheme'         => null,
			'processed_args' => null, // If used, should be a reference.
			'extra_attr'     => '',
		)
	);

	if ( is_numeric( $args['size'] ) ) {
		$args['size'] = absint( $args['size'] );
		if ( ! $args['size'] ) {
			$args['size'] = 96;
		}
	} else {
		$args['size'] = 96;
	}

	if ( is_numeric( $args['height'] ) ) {
		$args['height'] = absint( $args['height'] );
		if ( ! $args['height'] ) {
			$args['height'] = $args['size'];
		}
	} else {
		$args['height'] = $args['size'];
	}

	if ( is_numeric( $args['width'] ) ) {
		$args['width'] = absint( $args['width'] );
		if ( ! $args['width'] ) {
			$args['width'] = $args['size'];
		}
	} else {
		$args['width'] = $args['size'];
	}

	if ( empty( $args['default'] ) ) {
		$args['default'] = get_option( 'avatar_default', 'mystery' );
	}

	switch ( $args['default'] ) {
		case 'mm':
		case 'mystery':
		case 'mysteryman':
			$args['default'] = 'mm';
			break;
		case 'gravatar_default':
			$args['default'] = false;
			break;
	}

	$args['force_default'] = (bool) $args['force_default'];

	$args['rating'] = strtolower( $args['rating'] );

	$args['found_avatar'] = false;

	/**
	 * Filters whether to retrieve the avatar URL early.
	 *
	 * Passing a non-null value in the 'url' member of the return array will
	 * effectively short circuit get_avatar_data(), passing the value through
	 * the {@see 'get_avatar_data'} filter and returning early.
	 *
	 * @since 4.2.0
	 *
	 * @param array $args        Arguments passed to get_avatar_data(), after processing.
	 * @param mixed $id_or_email The Gravatar to retrieve. Accepts a user ID, Gravatar MD5 hash,
	 *                           user email, WP_User object, WP_Post object, or WP_Comment object.
	 */
	$args = apply_filters( 'pre_get_avatar_data', $args, $id_or_email );

	if ( isset( $args['url'] ) ) {
		/** This filter is documented in wp-includes/link-template.php */
		return apply_filters( 'get_avatar_data', $args, $id_or_email );
	}

	$email_hash = '';
	$user       = false;
	$email      = false;

	if ( is_object( $id_or_email ) && isset( $id_or_email->comment_ID ) ) {
		$id_or_email = get_comment( $id_or_email );
	}

	// Process the user identifier.
	if ( is_numeric( $id_or_email ) ) {
		$user = get_user_by( 'id', absint( $id_or_email ) );
	} elseif ( is_string( $id_or_email ) ) {
		if ( strpos( $id_or_email, '@md5.gravatar.com' ) ) {
			// MD5 hash.
			list( $email_hash ) = explode( '@', $id_or_email );
		} else {
			// Email address.
			$email = $id_or_email;
		}
	} elseif ( $id_or_email instanceof WP_User ) {
		// User object.
		$user = $id_or_email;
	} elseif ( $id_or_email instanceof WP_Post ) {
		// Post object.
		$user = get_user_by( 'id', (int) $id_or_email->post_author );
	} elseif ( $id_or_email instanceof WP_Comment ) {
		if ( ! is_avatar_comment_type( get_comment_type( $id_or_email ) ) ) {
			$args['url'] = false;
			/** This filter is documented in wp-includes/link-template.php */
			return apply_filters( 'get_avatar_data', $args, $id_or_email );
		}

		if ( ! empty( $id_or_email->user_id ) ) {
			$user = get_user_by( 'id', (int) $id_or_email->user_id );
		}
		if ( ( ! $user || is_wp_error( $user ) ) && ! empty( $id_or_email->comment_author_email ) ) {
			$email = $id_or_email->comment_author_email;
		}
	}

	if ( ! $email_hash ) {
		if ( $user ) {
			$email = $user->user_email;
		}

		if ( $email ) {
			$email_hash = md5( strtolower( trim( $email ) ) );
		}
	}

	if ( $email_hash ) {
		$args['found_avatar'] = true;
		$gravatar_server      = hexdec( $email_hash[0] ) % 3;
	} else {
		$gravatar_server = rand( 0, 2 );
	}

	$url_args = array(
		's' => $args['size'],
		'd' => $args['default'],
		'f' => $args['force_default'] ? 'y' : false,
		'r' => $args['rating'],
	);

	if ( is_ssl() ) {
		$url = 'https://secure.gravatar.com/avatar/' . $email_hash;
	} else {
		$url = sprintf( 'http://%d.gravatar.com/avatar/%s', $gravatar_server, $email_hash );
	}

	$url = add_query_arg(
		rawurlencode_deep( array_filter( $url_args ) ),
		set_url_scheme( $url, $args['scheme'] )
	);

	/**
	 * Filters the avatar URL.
	 *
	 * @since 4.2.0
	 *
	 * @param string $url         The URL of the avatar.
	 * @param mixed  $id_or_email The Gravatar to retrieve. Accepts a user ID, Gravatar MD5 hash,
	 *                            user email, WP_User object, WP_Post object, or WP_Comment object.
	 * @param array  $args        Arguments passed to get_avatar_data(), after processing.
	 */
	$args['url'] = apply_filters( 'get_avatar_url', $url, $id_or_email, $args );

	/**
	 * Filters the avatar data.
	 *
	 * @since 4.2.0
	 *
	 * @param array $args        Arguments passed to get_avatar_data(), after processing.
	 * @param mixed $id_or_email The Gravatar to retrieve. Accepts a user ID, Gravatar MD5 hash,
	 *                           user email, WP_User object, WP_Post object, or WP_Comment object.
	 */
	return apply_filters( 'get_avatar_data', $args, $id_or_email );
}