Memory leak - drawing text

[Thomas-2503]

Hi :)

I have found a memory leak when drawing text with Pillow.

How to reproduce

1. Pull a python docker image - I used python:3.8-slim
2. Install Pillow - I used version 10.1.0
3. Open an image via Pillow in a python script and just draw text (see code beneath)
4. Optional: Install psutils to output RAM usage
5. Run the docker image with the python script and use an image of your choice (test_pillow_image.png):

Docker run command (example)
docker run -it --rm --name pillow_python_test -v "$PWD":/usr/src/myapp -w /usr/src/myapp python_for_pillow python test_pillow.py

python_for_pillow is my docker python:3.8-slim image with Pillow (10.1.0) and psutils installed.

Python script to reproduce the memory leak (test_pillow.py)

import os
import time

from PIL import Image, ImageDraw

import psutil

if __name__ == '__main__':
    start_time = time.time()

    pid = os.getpid()
    process = psutil.Process(pid)

    while True:
        image = Image.open('test_pillow_image.png')
        image_draw = ImageDraw.Draw(image, 'RGBA')

        for i in range(0, 1000):
            image_draw.text((200, 200), 'Hi hi hi :)')

            if time.time() - start_time >= 10:  # output RAM usage every 10 seconds
                start_time = time.time()
                memory_info = process.memory_info()
                print(f'RAM usage: {memory_info.rss / 1000 / 1000} MB')

        image.close()

This code outputs the RAM usage every 10 seconds. Example output:

The RAM usage is increasing by approximately 2 MB every 10 seconds. This does not happen when drawing rectangles. If you replace the for loop with while true, the memory leak can be observed as well.

[muxamilian]

I can reproduce the leak.

[radarhere]

Ok, I've created PR #7549 to resolve this. See what you think.

[Thomas-2503]

Looks great, thank you :)