How do I save images in Messages to my hard drive?
This isn't quite as quick as a script via Mac, but if you know there are a few specific convos that have most of the images, you can access them all at once: 
- open message thread you want pics from
- keep scrolling up (tap on IOS clock to do quickly) as far back as you want pics
- tap on a photo
- once photo is open, you should be able to see a little "list" indicator on bottom right - 3 bullets &amp; lines
- tapping the list icon will open all photos from that date forward
- you can browse through &amp; save from there
- same procedure to take pics from camera roll &amp; save to mac from there

Apologies if this was already obvious to you or not quite the shortcut you were hoping for - but it's what I've found useful as I only have a few people that I regularly exchange lots of photos with!