wp_get_image_alttext( string $file ): string

1088function wp_get_image_alttext( $file ) {1089	$alt_text     = '';1090	$img_contents = file_get_contents( $file );1091 1092	if ( false === $img_contents ) {1093		return $alt_text;1094	}1095 1096	// Find the start and end positions of the XMP metadata.1097	$xmp_start = strpos( $img_contents, '<x:xmpmeta' );1098	$xmp_end   = strpos( $img_contents, '</x:xmpmeta>' );1099 1100	if ( false === $xmp_start || false === $xmp_end ) {1101		// No XMP metadata found.1102		return $alt_text;1103	}1104 1105	// Extract the XMP metadata from the JPEG contents1106	$xmp_data = substr( $img_contents, $xmp_start, $xmp_end - $xmp_start + 12 );1107 1108	// Parse the XMP metadata using DOMDocument.1109	$doc = new DOMDocument();1110	if ( false === $doc->loadXML( $xmp_data ) ) {1111		// Invalid XML in metadata.1112		return $alt_text;1113	}1114 1115	// Instantiate an XPath object, used to extract portions of the XMP.1116	$xpath = new DOMXPath( $doc );1117 1118	// Register the relevant XML namespaces.1119	$xpath->registerNamespace( 'x', 'adobe:ns:meta/' );1120	$xpath->registerNamespace( 'rdf', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#' );1121	$xpath->registerNamespace( 'Iptc4xmpCore', 'http://iptc.org/std/Iptc4xmpCore/1.0/xmlns/' );1122 1123	$node_list = $xpath->query( '/x:xmpmeta/rdf:RDF/rdf:Description/Iptc4xmpCore:AltTextAccessibility' );1124	if ( $node_list && $node_list->count() ) {1125 1126		$node = $node_list->item( 0 );1127 1128		// Get the site's locale.1129		$locale = get_locale();1130 1131		// Get the alt text accessibility alternative most appropriate for the site language.1132		// There are 3 possibilities:1133		//1134		// 1. there is an rdf:li with an exact match on the site locale.1135		// 2. there is an rdf:li with a partial match on the site locale (e.g., site locale is en_US and rdf:li has @xml:lang="en").1136		// 3. there is an rdf:li with an "x-default" lang.1137		//1138		// Evaluate in that order, stopping when we have a match.1139		$alt_text = $xpath->evaluate( "string( rdf:Alt/rdf:li[ @xml:lang = '{$locale}' ] )", $node );1140		if ( ! $alt_text ) {1141			$alt_text = $xpath->evaluate( 'string( rdf:Alt/rdf:li[ @xml:lang = "' . substr( $locale, 0, 2 ) . '" ] )', $node );1142			if ( ! $alt_text ) {1143				$alt_text = $xpath->evaluate( 'string( rdf:Alt/rdf:li[ @xml:lang = "x-default" ] )', $node );1144			}1145		}1146	}1147 1148	return $alt_text;1149}