Hide page title if the image field has a value
This method works for me. (Thanks to kim.kennof on Slack for the assistance.)

In my THEME.theme file:

function THEME_preprocess_page_title(&amp;$variables) {
  if ($node = \Drupal::routeMatch()-&gt;getParameter('node')) {
    if ($node instanceof \Drupal\node\Entity\Node) {
      $variables['node'] = $node;
    }
  }
}


Then in page-title.html.twig:

{% if node.field_image is empty %}
  {% if title %}
    &lt;h1{{ title_attributes.addClass('page-header') }}&gt;{{ title }}&lt;/h1&gt;
  {% endif %}
{% endif %}