pngcheck -v original.png (Shows chunk types and color depth)

"PNG to PNG better" sounds like a search engine riddle. After all, why would you convert a PNG to a PNG? Isn't that like re-filling a glass of water that is already full?

pngquant 256 --skip-if-larger --output step2.png -- step1.png

In the world of digital imaging, converting a PNG to another PNG isn't about changing the file format. It is about —taking an existing PNG and creating a new PNG that is smaller, sharper, cleaner, or more compatible than the original.