Create a full width attachment image in WordPress using Custom Post Types and Advanced Custom Fields

functions.php

add_action( 'after_setup_theme', 'setup' );
function setup() {
    add_theme_support( 'post-thumbnails' ); // This feature enables post-thumbnail support for a theme
    add_image_size( 'single-workspace', 9999, 840, false );
}

index.php

  <section class="workspace-header">
       <?php
         $image = get_field( 'featured_image');
         $size = 'single-workspace';
         $img = wp_get_attachment_image_src( $image, $size );
            echo '<div class="panel"';
               {
                 echo '<figure style="background-image: url(' . $img[0] . ')"></figure>';
               }
               echo '' . PHP_EOL;
         ?>
      <div class="row align-center">
              <span class="single-breadcrumbs workstation">
         <a href="<?php echo get_home_url(); ?>"> Home</a> &#47; <a href="<?php echo get_page_link(107); ?>">Workstations</a> &#47; <?php echo single_post_title(); ?>
        </span>
      </div>
      <div class="row align-center">
          <div class="workspace-block">
                  <h1 class="title"><span class="highlight"><?php the_title();?></span></h1><br>
                  <h2 class="title--sub font-primary"><span class="highlight--sub"><?php the_field('subtitle_workspace');?></span></h2>
            </div>
      </div>
    </section>

style.css

.panel{
  width:100%; height:100vh;
  max-height: 840px;
   background-position:center center;
   background-repeat:no-repeat;
   -webkit-background-size:cover;
   -moz-background-size:cover;
   -o-background-size:cover;
   background-size:cover;
  z-index:-1;
 display: block;
}

.workspace-block{z-index:400;margin-top:185px;}

.workspace-block h1 {
  font-size:3.813rem;
  font-weight: 700;
  position: relative;
   color:#212322;
   display: inline;
   background-color:#19ffff;
   padding:1px 11px 1px 11px;
}


.workspace-block h2{
font-size:1.688rem;
font-weight: 400;
   color:#212322;
font-family: 'Lato', sans-serif;
text-transform: uppercase;
display: inline-block;
 background-color:#19ffff;
padding:4px 8px 4px 8px;
}