hacks-guide-minimal-mistakes-theme/_includes/page__hero.html

{% if page.header.image contains "http" %}
  {% capture img_path %}{{ page.header.image }}{% endcapture %}
{% else %}
  {% capture img_path %}{{ page.header.image | prepend: "/images/" | prepend: base_path }}{% endcapture %}
{% endif %}

{% if page.header.overlay_image contains "http" %}
  {% capture overlay_img_path %}{{ page.header.overlay_image }}{% endcapture %}
{% elsif page.header.overlay_image %}
  {% capture overlay_img_path %}{{ page.header.overlay_image | prepend: "/images/" | prepend: base_path }}{% endcapture %}
{% endif %}

<div class="page__hero{% if page.header.overlay_color or page.header.overlay_image %}--overlay{% endif %}"
  style="background: {{ page.header.overlay_color | default: 'transparent' }} {% if overlay_img_path %}url('{{ overlay_img_path }}'){% endif %};"
>
  {% if page.header.overlay_color or page.header.overlay_image %}
    <div class="wrapper">
      <h1 class="page__title" itemprop="headline">
        {% if paginator %}
          {{ site.title }}{% unless paginator.page == 1 %} {{ site.data.ui-text[site.locale].page }} {{ paginator.page }}{% endunless %}
        {% else %}
          {{ page.title | markdownify | remove: "<p>" | remove: "</p>" }}
        {% endif %}
      </h1>
      {% if site.read_time and page.read_time %}<p class="page__meta"><i class="fa fa-clock-o" aria-hidden="true"></i> {% include read-time.html %}</p>{% endif %}
    </div>
  {% else %}
    <img src="{{ img_path }}" alt="{{ page.title }}" class="page__hero-image">
    {% if page.header.caption %}
      <span class="page__hero-caption">{{ page.header.caption | markdownify | remove: "<p>" | remove: "</p>" }}</span>
    {% endif %}
  {% endif %}
</div>