Display of Avatar Image in posts shown on an external site

Hello,

We are displaying community content on an external website using the REST API ( ex: latest blog articles + some additional criteria) . ActiveCast does not provide all query types we need to support so we are building a custom component that will pull content based on specific criteria using the REST API. Each post we display will have a title, author, date and avatar image. I would appreciate any help/guidance on the following:

1. If a user does not have an Avatar image, then what is passed by the API? Is there a placeholdert image that is assigned to users with no avatar image uploaded? If yes, can you please point me to it so i know what it would look like on our website?

2. Avatar images uploaded by users consist of various aspect ratios? For consistency, is there a way to render the avatar on the website with a standard 1:1 aspect ratio?

Thanks,

Manasa