Ok, it’s as simple as:
{% set post_image = Image(678) %}
<img src="https://wordpress.stackexchange.com/questions/352244/{{ post_image.src }}" alt="{{ post_image.alt }}" srcset="https://wordpress.stackexchange.com/{{ post_image.srcset }}" sizes="{{ post_image.img_sizes }}" />
Ref: Twig set