For those interested how to do media collections, I just implemented a scheme were we can add taxonomy to images (and other media files) in a corresponding image.meta.yaml file like this:
someimage.jpg.meta.yaml:
alt: Information
taxonomy:
tag: [sidebar]
category: [landscape]
basename: info-box
and then using a wildcard Twig filer which allows using the taxonomy class as wildcard
new \Twig_SimpleFilter('has_*', [$this, 'has_filter']),
public function has_filter($class, $mediaCollection, $key)
{
$result = [];
foreach ($mediaCollection as $item) {
if (in_array($key, $item->taxonomy[$class])) {
$result[] = $item;
}
}
return $result;
}
and a template to render:
{% set sidebar = page.media.images|has_tag('sidebar')|first %}
{% if sidebar %}
...
<img width="300" src="{{ sidebar.resize(300, 0).url }}" alt="{{ sidebar.alt }}">
...
{% endif %}