How to convert PNG to JPG on Mac. You can save PNG files as JPGs in a number of common Mac apps, but the easiest is to use Preview. 1. Start Finder and then locate the PNG file you want to convert. 2.

$ file iphone-id.png iphone-id.png: PNG image data, 470 x 118, 8-bit/color RGB, non-interlaced Where identify really shines is with JPEG files, which the file command can't quite seem to figure out.