heic2png is a cli app that losslessly transcodes heic images to png.
It includes options to automatically batch all the .heic files it finds in a folder, and can spread the work across all available CPU cores. Currently, it only outputs png, and only with minimal compression to keep it fast. Note that this may result in relatively large png files (which, imo, is preferrable to spending a bunch of time trying to compress image data that likely won't compress very well anyway).
Download the latest release, and then put the exe somewhere in your path.
Run heic2png -h to see all the flags and arguments. As of v0.2.0, your output should look something like this:
$ heic2png -h
Usage of heic2png:
-a, --all · · · · · find all *.heic files and convert them to *.png
--delete · · · · · delete original heic file after successfull conversion
-f, --file <filename> specify a single heic file to convert to .png
--overwrite · · · · if target png file already exists, overwrite it
-p, --procs <num_procs> max number of files to process in parallel (defaults to number of available cores)
-v, --version · · · · · print version information and exit
-h, --help · · · · · print this message and exit
For whatever reason, I prefer my phone to be Apple, but my desktop to be PC. These days iPhones create photos using HEIC, but Windows doesn't really have good first-party support yet. Up until now, I've been using Irfanview to losslessly batch convert HEIC files to PNG, but the problem with Irfanview is it is single-threaded, so it takes a lot longer than it should to run through a large folder.