get featured image URL

featured image URL

<?php 
    if (has_post_thumbnail( $post->ID ) ) {
    $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'single-post-thumbnail' ); 
?>
<section id="masthead">
    <img src="<?php echo $image[0]; ?>" alt="<?php the_title(); ?>" class="scale-with-grid">
</section>
<?php 
    }
?>