functions.php

<?php

/**
 * Use Genesis Image in Yoast Schema 
 * If no featured image is specified, genesis_get_image() uses first uploaded to post 
 *
 * @see https://www.billerickson.net/code/yoast-schema-use-genesis-image/
 */
function be_yoast_schema_use_genesis_image( $graph_piece ) {

	if( ! is_singular() )
		return $graph_piece;

	if( empty( $graph_piece['image'] ) && function_exists( 'genesis_get_image' ) ) {
		$image = genesis_get_image( array( 'format' => 'url' ) );
		if( !empty( $image ) )
			$graph_piece['image'] = array(
				'@id' => $image . '#primaryimage',
				'@type' => 'ImageObject',
				'url' => $image,
			 );
	}
	return $graph_piece;
};
add_filter( 'wpseo_schema_article', 'be_yoast_schema_use_genesis_image' );