Custom header snippet for wordpress

gistfile1.php

<?php
$defaults = array(
    'default-image'   => get_template_directory_uri() . '/assets/img/logo.png',
    'flex-height'     => true,
    'flex-width'      => true,
    'width'           => 280,
    'height'          => 70,
    'header-text'     => false,
    'uploads'         => true,
);

add_theme_support( 'custom-header', $defaults );
?>

<a class="brand" href="<?php echo home_url(); ?>/"><img src="<?php header_image(); ?>" height="<?php echo get_custom_header()->height; ?>" width="<?php echo get_custom_header()->width; ?>" alt="<?php bloginfo('name'); ?>" /></a>