The default photo format of iPhones. If that's important. Support was added to imagemagick a year-or-so ago.

In imagemagick, a HEIC image of quality "75" is approximately the same file size as an image of JPEG quality "95".

For the same quality "number", HEIC images are often larger than their JPEG equivalents, which can be confusing if you assume the number directly indicates a "quality" level, which it apparently doesn't.