Apple's Workflow app allows you to create a variety of automations on your iPhone or iPad. An example is a workflow that takes a video from your library and creates an animated GIF from it. You can store this in your Photos app even though Photos doesn't display the animation. You can then share it online instead of the video.
Is there an app for iMac?
Kika: An app to create GIFs? Many. Just search the app store. I did a video on one a while ago: https://macmost.com/creating-animated-gifs.html
can you do this with automator on your mac?
Jeff: There's no Animated GIF export action in Automator, so no, not really. But many ads install their own Automator actions, so it is possible that one such app will add this to Automator. But there are plenty of GIF-maker apps for the Mac if that is your goal. This tutorial merely displays another use for Workflow.