An override for search results to show images in article results . put in /templates/your_template/html/com_search/search

default_results.php

<?php
/**
* @package     Joomla.Site
* @subpackage  com_search
*
* @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
* @license     GNU General Public License version 2 or later; see LICENSE.txt
*/
defined('_JEXEC') or die;
$db = JFactory::getDBO();
$db->setQuery("SELECT * FROM #__content ORDER BY created DESC");
$articles = $db->loadObjectList();
?>
<dl class="search-results<?php echo $this->pageclass_sfx; ?>">
<?php foreach ($this->results as $count=>$result) : ?>
<div class="item-result">
<dt class="result-title">
        <?php echo $this->pagination->limitstart + $result->count . '. '; ?>
        <?php if ($result->href) : ?>
            <a href="<?php echo JRoute::_($result->href); ?>"<?php if ($result->browsernav == 1) : ?> target="_blank"<?php endif; ?>>
                <?php                 // $result->title should not be escaped in this case, as it may ?>
                <?php                 // contain span HTML tags wrapping the searched terms, if present ?>
                <?php                 // in the title. ?>
                <?php echo $result->title; ?>
            </a>
        <?php else : ?>
            <?php             // see above comment: do not escape $result->title ?>
            <?php echo $result->title; ?>
        <?php endif; ?>
    </dt>
    <?php if ($result->section) : ?>
        <dd class="result-category">
            <span class="small<?php echo $this->pageclass_sfx; ?>">
                (<?php echo $this->escape($result->section); ?>)
            </span>
        </dd>
    <?php endif; ?>
    <dd class="result-text">
          <?php
          foreach ($articles as $article) {
            $article_href[$count] = 'index.php?option=com_content&view=article&id=' . $article->id . ':' . $article->alias . '&catid=' . $article->catid;
            if ($article_href[$count] == $result->href) {
              $article_images[$count] = json_decode($article->images);
        //Para pegar a primeira imagem em qualquer parte de um texto dos artigos
              preg_match('/(?<!_)src=([\'"])?(.*?)\\1/', $article->introtext.$article->fulltext, $matches);
              $image_in_article[$count] = $matches[2];

            if ($image_in_article[$count]) {
              $theimage[$count] = $image_in_article[$count];
            }
            elseif (($article_images[$count]->image_intro) and (empty($article_images[$count]->image_fulltext) or empty($image_in_article[$count])))   {
              $theimage[$count] = $article_images[$count]->image_intro;
            }

            elseif (($article_images[$count]->image_fulltext) and (empty($article_images[$count]->image_intro) or empty($image_in_article[$count])))   {
              $theimage[$count] = $article_images[$count]->image_fulltext;
            }
            elseif ($image_in_article[$count] and (empty($article_images[$count]->image_fulltext) or empty($article_images[$count]->image_intro)))   {
              $theimage[$count] = $image_in_article[$count];
            }
           echo '<div class="article_image_search"><a href="'.JRoute::_($result->href).'"><img src="'.$theimage[$count].'" alt="'.$article->title.'" /></a></div>';

           }
          }

        ?>
        <?php echo $result->text; ?>
    </dd>
    <?php if ($this->params->get('show_date')) : ?>
        <dd class="result-created<?php echo $this->pageclass_sfx; ?>">
            <?php echo JText::sprintf('JGLOBAL_CREATED_DATE_ON', $result->created); ?>
        </dd>
    <?php endif; ?>
    </div>
<?php endforeach; ?>
</dl>
<div class="pagination">
    <?php echo $this->pagination->getPagesLinks(); ?>
</div>