您需要先打开/加载图像，如下所示:

You need to open/load the image first... like this:

#!/usr/local/bin/python3

import numpy as np
from PIL import Image, ImageDraw, ImageFont

# Open input image
im = Image.open('image.png').convert('RGB')

# Get a drawing context
draw = ImageDraw.Draw(im)

pixellat=ImageFont.truetype("/Library/Fonts/Apple Chancery.ttf",48)
draw.text((80, 40),"This is a test",(255,255,255),font=pixellat)

# Save
im.save('result.png')