File format of image downloaded SharePoint Site Web API

I want to know the format of the image file that is retrieving using this API url from Sharepoint.
https://xxx.sharepoint.com/sites/projectXYZ/_api/web/GetFileByServerRelativeUrl('/sites/projectXYZ/Documents/Index/dog.png')/$value

I am able to hit this API, but the value is returned in a diff format. Please see the image.

What is the file format? Is it base64 or something else?
I want to bind this file to a Power Apps PCF html control. How can I bind this to a html control? Thank you.