Register Custom Featured Image Size for Page in Genesis

functions.php

<?php
// Do NOT include the opening PHP tag

// Register a custom image size for Singular Page Featured images
add_image_size( 'singular-page-featured-thumb', 1277, 300, true );

// Display image before content-sidebar-wrap
add_action( 'genesis_before_content_sidebar_wrap', 'page_display_featured_image' );
function page_display_featured_image() {
	if ( ! is_singular( array( 'page' ) ) ) {
		return;
	}
	if ( ! has_post_thumbnail() ) {
		return;
	}
	// Display featured image above content
	echo '<div class="singular-page-featured color-gradient mobile-hide">';
		genesis_image( array( 'size' => 'singular-page-featured-thumb' ) );
	echo '</div>';
}