convert.py

# convert a .png image file to a .bmp image file using PIL

from PIL import Image
import os

for file in os.listdir("."):
    file_in = file
    if ".png" in file:
        img = Image.open(file_in)


        file_out = file.replace(".png", ".bmp")
        print (len(img.split()))  # test
        if len(img.split()) == 4:
            # prevent IOError: cannot write mode RGBA as BMP
            r, g, b, a = img.split()
            img = Image.merge("RGB", (r, g, b))
            img.save(file_out)
        else:
            img = img.convert(mode="P", palette=Image.WEB)
            img.save(file_out)