import glob import PIL.Image photos = glob.glob('photos/*.jpg') for image in photos: img = PIL.Image.open(image) img.save(image.replace('.jpg', '.webp')) ratio = 200/max(img.height, img.width) img.resize((int(img.width * ratio), int(img.height * ratio))) image = image.replace('photos/', 'photos/thumbnail/').replace('.jpg', '.webp') img.save(image, quality=10, subsampling=2)