Fix deprecation warning about ImageFont.getsize

[brvoisin]

python-barcode/barcode/writer.py:441: DeprecationWarning: getsize is
deprecated and will be removed in Pillow 10 (2023-07-01). Use getbbox
or getlength instead.
width, height = font.getsize(subtext)

ImageFont.getsize is deprecated since the version 9.2 of Pillow. We
use anchor instead of computing the right position to have an aligned
text.

It is related to the issue #163.
The solution was suggested by @nulano (contributor of Pillow).

[brvoisin]

I tested with this script test.py:

import sys

from barcode import generate
from barcode.writer import  ImageWriter

with open(sys.argv[1], "wb") as f:
    generate("CODE128", "My super test", writer=ImageWriter(), output=f)

The image is slightly different.

Also, anchor doesn't work with Pillow 7. I tested with the version 9, 8 and 7.

[brvoisin]

I fixed the test position by using the anchor md (middle descender) instead of ms (middle baseline). See https://pillow.readthedocs.io/en/stable/handbook/text-anchors.html#text-anchors to understand what it means.

Before:

After:

[codecov]

Codecov Report

Merging #165 (e1de637) into main (77c902f) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #165      +/-   ##
==========================================
- Coverage   80.60%   80.58%   -0.03%     
==========================================
  Files          17       17              
  Lines         887      886       -1     
==========================================
- Hits          715      714       -1     
  Misses        172      172              

Impacted Files	Coverage Δ
barcode/writer.py	95.04% <100.00%> (-0.03%)	⬇️

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[WhyNotHugo]

Perfect. I can't even tell the difference in the results (if there is any).

Nice cleanup, thanks for your contribution!