Just had a response from Will Woodgate. Here it is in it’s entirety. Hopefully it will come through:
Hi Jody,
Yes this is perfectly possible in ImageMagic already, if you’re okay to sacrifice support for downloads in Safari. The trick is to give your linked image a custom attribute of download, like in the attached screenshot, when you are setting your image link.
Then when someone clicks the link in Chrome, Firefox, Opera or Internet Explorer Edge, the file you link to will download instead of open in a new browser window or tab. It’s very easy to do and works reliably. But for some reason Safari has not added support for this yet, so the link will still open in the browser window instead of download.
You can read more about the download attribute here:
I have attached an example project file to this email too that you can preview and test in Chrome or Firefox. You should find the text file I have linked to downloads.
Regards,
Will.