print image files to thermal printer ESC-POS on stdout

esc-pos-image.py

#!/usr/bin/env python3
# esc-pos-image.py - print image files given as command line arguments
#                    to simple ESC-POS image on stdout
# scruss - 2014-07-26 - WTFPL (srsly)
#        - 2021-01-09 (made python3 compatible - tvm Carko!)

# if you want a proper CUPS driver for a 58mm thermal printer
# that uses this command set, go here:
#            https://github.com/klirichek/zj-58

import sys
from PIL import Image
import PIL.ImageOps
import struct

# give usage and exit if no arguments
if (len(sys.argv) == 1):
    print('Usage:', sys.argv[0],
          'image1 image2 ... [ > printer_device ]')
    exit(1)

# print all of the images!
for i in sys.argv[1:]:
    im = Image.open(i)

    # if image is not 1-bit, convert it
    if (im.mode != '1'):
        im = im.convert('1')

    # if image width is not a multiple of 8 pixels, fix that
    if (im.size[0] % 8):
        im2 = Image.new('1', (im.size[0] + 8 - im.size[0] % 8,
                              im.size[1]), 'white')
        im2.paste(im, (0, 0))
        im = im2

    # Invert image, via greyscale for compatibility
    #  (no, I don't know why I need to do this)
    im = PIL.ImageOps.invert(im.convert('L'))
    # ... and now convert back to single bit
    im = im.convert('1')

    # output header (GS v 0 \000), width, height, image data
    sys.stdout.buffer.write(b''.join((bytearray(b'\x1d\x76\x30\x00'),
                                      struct.pack('2B', int(im.size[0] / 8) % 256,
                                                  int(im.size[0] / (8 * 256))),
                                      struct.pack('2B', im.size[1] % 256,
                                                  int(im.size[1] / 256)),
                                      im.tobytes())))

python-escpos didn't used to work for me, so I'm glad to see that it's getting some attention

it works for me, but maybe a bit too well... and by that I mean running python-escpos takes over control of the USB device and never hands it back (even using close()), so I can't use the simple printf "hi\n\n\n" > /dev/usb/lp0 after using it, and have to restart the printer to do so. Ah well, I guess I will do everything using the python library... >:(