Wordpress blog page featured image

Question

I like to use the page's featured images in a background image in the header. When I add a new page and set the featured image, it appears as background image works exactly what I wanted. But on a Blog main page (the Home, page of displaying posts) I set the featured image and in the header display the first post's featured image insetad the one I set at the page's featured image. Tried to find solution, but nothing works, don't know how to magae it. Here is my code that handle background image:

<div class="sub-header"
    <?php
        if (has_post_thumbnail( $post->ID ) ):
            $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'single-post-thumbnail' );
            echo 'style="background-image: url(\'';
            echo $image[0];
            echo '\');"';
        endif;
    ?>
    >
</div>

Answer 1

Make the custom image source, whether it's assigned in the customizer or hard coded.