BUG: Unable to create font using jpg

• Traceback:

❯ handwrite Downloads/sa\ handwrite\ font_1\ \(1\).jpg .
Traceback (most recent call last):
  File "/home/saahil/anaconda3/envs/handwrite/bin/handwrite", line 8, in <module>
    sys.exit(main())
  File "/home/saahil/anaconda3/envs/handwrite/lib/python3.7/site-packages/handwrite/cli.py", line 57, in main
    args.input_path, args.output_directory, args.directory, args.config, metadata
  File "/home/saahil/anaconda3/envs/handwrite/lib/python3.7/site-packages/handwrite/cli.py", line 34, in converters
    run(sheet, output_directory, directory, config, metadata)
  File "/home/saahil/anaconda3/envs/handwrite/lib/python3.7/site-packages/handwrite/cli.py", line 12, in run
    SHEETtoPNG().convert(sheet, characters_dir, config)
  File "/home/saahil/anaconda3/envs/handwrite/lib/python3.7/site-packages/handwrite/sheettopng.py", line 49, in convert
    characters_dir,
  File "/home/saahil/anaconda3/envs/handwrite/lib/python3.7/site-packages/handwrite/sheettopng.py", line 160, in save_images
    images[0],
cv2.error: OpenCV(4.5.4) /tmp/pip-req-build-3129w7z7/opencv/modules/imgcodecs/src/loadsave.cpp:799: error: (-215:Assertion failed) !_img.empty() in function 'imwrite'

• Dependencies:

❯ fontforge -v
Copyright (c) 2000-2021. See AUTHORS for Contributors.
 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
 with many parts BSD <http://fontforge.org/license.html>. Please read LICENSE.
 Version: 20201107
 Based on sources from 2021-11-27 12:18 UTC-ML-D-GDK3.
 Based on source from git with hash: 58238cc173c80379d0d4616971fc793da26c6aa4
fontforge 20201107
build date: 2021-11-27 12:18 UTC

❯ potrace -v
potrace 1.16. Copyright (C) 2001-2019 Peter Selinger.
Library version: potracelib 1.16
Default unit: inches
Default page size: letter

❯ conda list
# packages in environment at /home/saahil/anaconda3/envs/handwrite:
#
# Name                    Version                   Build  Channel
_libgcc_mutex             0.1                        main  
_openmp_mutex             4.5                       1_gnu  
ca-certificates           2021.10.26           h06a4308_2  
certifi                   2021.10.8        py37h06a4308_0  
handwrite                 0.3.0                    pypi_0    pypi
ld_impl_linux-64          2.35.1               h7274673_9  
libffi                    3.3                  he6710b0_2  
libgcc-ng                 9.3.0               h5101ec6_17  
libgomp                   9.3.0               h5101ec6_17  
libstdcxx-ng              9.3.0               hd4cf53a_17  
ncurses                   6.3                  h7f8727e_2  
numpy                     1.21.4                   pypi_0    pypi
opencv-python             4.5.4.60                 pypi_0    pypi
openssl                   1.1.1l               h7f8727e_0  
pillow                    8.4.0                    pypi_0    pypi
pip                       21.2.2           py37h06a4308_0  
python                    3.7.11               h12debd9_0  
readline                  8.1                  h27cfd23_0  
setuptools                58.0.4           py37h06a4308_0  
sqlite                    3.36.0               hc218d9a_0  
tk                        8.6.11               h1ccaba5_0  
wheel                     0.37.0             pyhd3eb1b0_1  
xz                        5.2.5                h7b6447c_0  
zlib                      1.2.11               h7b6447c_3  

• Images used:

Fitted to A4 size using Adobe Scan

Original image scanned using Adobe Scan

• Operating system used:

❯ neofetch 
██████████████████  ████████   saahil@saahil-gl638rd 
██████████████████  ████████   --------------------- 
██████████████████  ████████   OS: Manjaro Linux x86_64 
██████████████████  ████████   Host: GL63 8RD REV:1.0 
████████            ████████   Kernel: 5.10.79-1-MANJARO 
████████  ████████  ████████   Uptime: 4 hours, 59 mins 
████████  ████████  ████████   Packages: 1564 (pacman) 
████████  ████████  ████████   Shell: bash 5.1.8 
████████  ████████  ████████   Resolution: 1920x1080 
████████  ████████  ████████   WM: i3 
████████  ████████  ████████   Theme: Matcha-dark-sea [GTK2], Numix [G 
████████  ████████  ████████   Icons: Papirus-Dark [GTK2/3] 
████████  ████████  ████████   Terminal: kitty 
████████  ████████  ████████   CPU: Intel i7-8750H (12) @ 4.100GHz 
                               GPU: NVIDIA GeForce GTX 1050 Ti Mobile 
                               GPU: Intel CoffeeLake-H GT2 [UHD Graphi 
                               Memory: 3189MiB / 15850MiB

• Tried both conda and python venv environments, but it failed in both with the same error shared above.
• Python version 3.7

Reproduce the failure with the reported handwrite JPG command, then inspect handwrite/cli.py and handwrite/sheettopng.py, especially save_images at the reported line. Confirm what produces the empty image passed to OpenCV and verify that the command generates the expected font without the imwrite error.