Enabling Download of Photos On My Website

Hello! Is there a way I can allow my website visitors to download/ save a picture I've posted?

Do I need a Custom CSS for it?

Users can right click an image and see an option to download. 

However, this will download the size optimised version that Squarespace serves up which could be smaller that the original. 

To allow downloading of the original get the address of the image on the page (right click and Copy image address).

Paste the address into a document then chop off anything from ?format= to the end of the address (?format=750w in the example below)

Copy the modified image address and use it as the link for a Squarespace button. Set the link to open in a new window. Depending on the user's browser settings it will open in a new window or prompt to download. 

This is super helpful, (thank you) but my mac browser opens image in a new window. Other than creating a zip file - is there a way to force browser to download this?