Here's how to link the article intro images, on a category blog page for example, to its article like the article title or "Read more" links.

Copy

JOOMLA-ROOT/layouts/joomla/content/intro_image.php

to

JOOMLA-ROOT/templates/<YOUR_TEMPLATE>/html/layouts/joomla/content/intro_image.php

You may have to create some or all of the folders—html, layouts, joomla, and content—inside your template folder. Then simply control-drag intro_image.php into that folder.

Then, edit the code in that new override file by wrapping the image tag with:

<a href="/<?php echo JRoute::_(ContentHelperRoute::getArticleRoute($displayData->slug, $displayData->catid)); ?>" itemprop="url"> </a>

The <img /> tag will have a bunch of php code in the middle of it, so you have to figure out where the end is and place the closing anchor tag after that.