how to change jpg to png on macOS

You can create an Applications -> Automator app

Using the "Change Type of Image"

Then just drag and drop the JPG image on top of the app you create with Automator, and the converted files will appear on your Desktop

http://osxdaily.com/2010/01/12/convert-png-to-jpg-or-convert-jpg-to-png/

more

https://www.google.com/search?source=hp&ei=HW7iXIGBBZHxkwXXoq_YCQ&q=mac+convert+jpg+to+png&oq=mac+convert+jpg+to+png&gs_l=psy-ab.12..0j0i22i30l9.39.39..244...0.0..1.151.254.0j2......0....2j1..gws-wiz.....0.H6HzooUqNjo

If you want to really "Geek" out, and you are comfortable with the command line, you can use the /usr/bin/sips command to convert, resize, and do other image processing. Experimentation and Googling would be necessary to get the desired results with sips, but once you have what you want you can put that into an Automator app and invoke sips via a "Run Shell Script" Automator action.

Or have a shell script with your sips command in it.

Right click on the image.

Open with - Preview

Once opened in Preview:

File - Export

Select PNG from the drop down menu,

The online tool that helps you convert jpg to png files that I have collected and used on mac is: https://jpg4png.com/

:)