python给图片右上角加上红色的数字

from PIL import Image,ImageDraw,ImageFont

def addNum(filePath):
    img = Image.open(filePath)
    size = img.size
    fontSize = size[1] / 4
    draw = ImageDraw.Draw(img)
   
    ttFont = ImageFont.truetype("/Library/Fonts/arial.ttf", fontSize)
    draw.text((size[0]-fontSize, 0), "3",(256,0,0), font=ttFont)
    del draw
    img.save('./result.jpg')
    img.show()

print addNum("image.jpg")