Pillow, how to put the text in the center of the image

Question

I use the Pillow (PIL) 6.0 and add text in the image. And I want to put the text in the center of the image. Here is my code,

import os
import string
from PIL import Image
from PIL import ImageFont, ImageDraw, ImageOps

width, height = 100, 100

text = 'H'
font_size = 100

os.makedirs('./{}'.format(text), exist_ok=True)

img = Image.new("L", (width, height), color=0)   # "L": (8-bit pixels, black and white)
font = ImageFont.truetype("arial.ttf", font_size)
draw = ImageDraw.Draw(img)
w, h = draw.textsize(text, font=font)
draw.text(((width-w)/2, (height-h)/2), text=text, fill='white', font=font)

img.save('H.png')

Here is the output:

Question:

The text is in the center horizontally, but not in the center vertically. How can I put it in the center horizontally and vertically?

Answer 1

Text always have some added space around characters, e.g. if we create a box that is the exact size reported for your 'H'

img = Image.new("L", (width, height), color=0)   # "L": (8-bit pixels, black and white)
font = ImageFont.truetype("arial.ttf", font_size)
draw = ImageDraw.Draw(img)
w, h = draw.textsize(text, font=font)
# draw.text(((width-w)/2, (height-h)/2), text=text, fill='white', font=font)
# img.save('H.png')
img2 = Image.new("L", (w, h), color=0)   # "L": (8-bit pixels, black and white)
draw2 = ImageDraw.Draw(img2)
draw2.text((0, 0)), text=text, fill='white', font=font)
img2.save('H.png')

gives the bounding box:

Knowing that line height is normally ~20% larger than the glyphs/characters (+ some trial and error), and we can figure out the extent of the extra space. (The extra space for width is equally distributed so not interesting for centering).

draw2.text((0, 0 - int(h*0.21)), text=text, fill='white', font=font)

which moves the 'H' to the top:

Plugging this back into your original code:

img = Image.new("L", (width, height), color=0)   # "L": (8-bit pixels, black and white)
font = ImageFont.truetype("arial.ttf", font_size)
draw = ImageDraw.Draw(img)
w, h = draw.textsize(text, font=font)
h += int(h*0.21)
draw.text(((width-w)/2, (height-h)/2), text=text, fill='white', font=font)
img.save('H.png')

gives:

The 0.21 factor usually works well for a large range of font sizes for the same font. E.g. just plugging in font size 30: