how to get uri of an image field in a views_view_list twig template using drupal 8?
Finally this was my solution.

The template:

&lt;div class="slider-container"&gt;
  &lt;div class="slider-fullwidth"&gt;
    &lt;{{ list.type }}{{ list.attributes }}&gt;

      {% for row in rows %}
      &lt;li{{ row.attributes }}
        data-thumb="{{ row.content['#slider'].field_background_image|imagestyleurl2('slider_thumbnail') }}"
        data-title="{{ row.content['#slider'].title[0].value }}"
        data-transition="slideup"&gt;{{ row.content }}&lt;/li&gt;
      {% endfor %}

    &lt;/{{ list.type }}&gt;
  &lt;/div&gt;
&lt;/div&gt;


Twig filter:

class ImageStyleTwig extends \Twig_Extension
  {

/**
 * Generates a list of all Twig filters that this extension defines.
 */
public function getFilters()
{
  return [
    new \Twig_SimpleFilter('imagestyleurl1', array($this, 'imageStyleUrl1')),
    new \Twig_SimpleFilter('imagestyleurl2', array($this, 'imageStyleUrl2')),
  ];
}


/**
 * Gets a unique identifier for this Twig extension.
 */
public function getName()
{
  return 'imagestyle.mymodule_general.twig_extension';
}


/**
 * Get the url of the image by an image style
 */
public static function imageStyleUrl1($imageField, $imageStyle)
{
  return ImageStyle::load($imageStyle)-&gt;buildUrl($imageField[0]['#item']-&gt;entity-&gt;uri-&gt;value);
}


public static function imageStyleUrl2($imageField, $imageStyle)
{
  return ImageStyle::load($imageStyle)-&gt;buildUrl($imageField-&gt;entity-&gt;uri-&gt;value);
}


}