custom image/file attribute in composer - how to make image size responsive?

I hope some of you are able to help me with this annoying problem.

I have created at simple blog. On the blog entry page I have a custom attribute 'blog_image', which is used for both a top parallax image and a smaller image on page.

The image on page I've placed using the block 'Edit Page Attribute Display'. This allows you to set with and height in pixel. But what if I want this to be responsive?
How do I do this?

View Replies:
AncaV replied on at Permalink Reply
Try using something like this in your style:
width:100%; (or whatever you want it to be)
height: auto;
Maybe it will be necessary to specify !important on those two in order for them to work.
tilde replied on at Permalink Reply
Thanks for your reply...

Yes, of course one can style the image through css, but what I am looking for is a way to render the picture directly with the right output format.

That is, how can you apply a custom template for the output of an image generated through the Edit Page Attribute Display block?
MrKDilkington replied on at Permalink Reply

Are you referring to the <picture> element?