How to get Alarm images in alarm emails

The Zoneminder documentation for Options => Emails gives a list of tags that one can set on a filter so that the selected tags are entered in the email. The page also contains the warning "Todo - check if any other tags have been added".

I wanted to see the alarmed emails, where the alarmed area is marked in the alarm colour set in the zone definition. The documentation for available tags (Options => Emails) does not give a tag for this. I therefore inspected the code in zmfilter.pl. This file, normally found in /usr/bin/, controls the checking of filters and the sending of emails.