Pillow用法

pip install pillow

from PIL import Image

img = Image.open("filename.jpg")

from io import BytesIO

img = Image.open(BytesIO(b"..."))

print(img.format)
print(Image.MIME[img.format])

width, height = img.size
img = img.resize((int(width/2), int(height/2)))

img = img.convert("L")

img.save("filename.jpg")