add metadata png PIL
from PIL.PngImagePlugin import PngImageFile, PngInfo
targetImage = PngImageFile("pathToImage.png")
metadata = PngInfo()
metadata.add_text("MyNewString", "A string")
metadata.add_text("MyNewInt", str(1234))
targetImage.save("NewPath.png", pnginfo=metadata)
targetImage = PngImageFile("NewPath.png")
print(targetImage.text)
>>> {'MyNewString': 'A string', 'MyNewInt': '1234'}