Oh man, converting 1200 images one by one? Ain't nobody got time for that! If you want to convert HEIC files to PNG on your Mac in batch, you can use the command line. I'll give you the command line method, which is pretty efficient and doesn't require additional software.
Here’s a step-by-step guide to doing it via Terminal:
- Step 1. Open Terminal: You can find it in the Utilities folder within your Applications folder or search for it using Spotlight.
- Step 2. Navigate to the Folder: Use the cd command to navigate to the folder where your HEIC files are stored. For example:
cd /path/to/your/heic/images
- Step 3. Run the Conversion Command: Use the following command to convert all HEIC files in the folder to PNG:
mogrify -format png *.HEIC

NOTE: This command requires ImageMagick, a powerful image manipulation tool that you can install via Homebrew with the command brew install imagemagick if you don’t have it already.
If Command Line isn't doing the trick for you, there are some alternative routes you can take:
Third-Party Apps: There are a bunch of apps out there designed for batch image conversion. You mentioned you're okay with recommendations, so "TunesBro HEIC Converter" is a popular one that's user-friendly. Another one is "Permute" - it's not free, but it's pretty powerful for media conversion tasks.
Source: https://www.uubyte.com/blog/batch-convert-heic-to-png-on-mac/

2. Online Services: If you don’t mind uploading your photos to a web service, websites like CloudConvert or HEICtoJPEG can bulk convert your images. Just be mindful of privacy and terms of service, especially with personal photos.

Always make sure you have a backup before you start the process, just in case something goes awry. And if you go for an app or online service, check out some reviews first to make sure it’s legit and suits your needs.