I've also used ImageMagick, at the suggestion of people on the Mathworks Image Processing toolbox team. I got the images from someone with a iPhone who didn't know she had options for how to format the image for sending. She could have used a different format but HEIC was the default. She didn't need to resnap, just needed to adjust some settings before transmitting, like this:
It’s easy on the Mac. For interactive use, use the Preview app to export any image to another format. For command-line scripting, use /usr/bin/sips.
For iPhone users, change a setting in order to share photos as JPEG rather than HEIC:
Settings -> Photos -> Transfer to Mac or PC -> Automatic
The IPT team knows about the issue (for a long time now) and it's on their to-do list. In fact many of them use Apple products. They said that requests sent in to firstname.lastname@example.org influence their priority list, so let's have everyone send in their request to have read (especially) and write capability for HEIC format image files.