friendica/view/templates/content/image/single_with_height_allocation.tpl

{{* The padding-top height allocation trick only works if the <figure> fills its parent's width completely or with flex. 🤷‍♂️
	As a result, we need to add a wrapping element for non-flex (non-image grid) environments, mostly single-image cases.
 *}}
{{if $allocated_max_width}}
<div style="max-width: {{$allocated_max_width|default:"auto"}};">
{{/if}}

<figure class="img-allocated-height" style="width: {{$allocated_width|default:"auto"}}; padding-bottom: {{$allocated_height}}">
    {{if $image->preview}}
		<a data-fancybox="uri-id-{{$image->uriId}}" href="{{$image->url}}">
			<img src="{{$image->preview}}" alt="{{$image->description}}" title="{{$image->description}}" loading="lazy">
		</a>
    {{else}}
		<img src="{{$image->url}}" alt="{{$image->description}}" title="{{$image->description}}" loading="lazy">
        {{if $image->description}}
		    <figcaption>{{$image->description}}</figcaption>
        {{/if}}
    {{/if}}
</figure>

{{if $allocated_max_width}}
</div>
{{/if}}