Print lamp ID labels on the Brother QL-820NWB

label_printer.py renders a DK-11221 23x23 mm label (QR code linking
to the lamp's buildfor.life page plus the ID) and sends it over the
network backend (brother-ql-next). The station prints two after each
successful measurement, one for the box and one for the lamp; printer
failures never lose a run, and any lamp can be reprinted with
uv run label_printer.py <ID>. Printer address via HPCS_LABEL_PRINTER
or --printer.

README.md

@@ -110,7 +110,11 @@ from the packaging (flux, CCT, power, CRI, lifetime, equivalent W -> stored
 under "rated" in metrics.json for claimed-vs-measured comparison), insert the
 lamp, and the tool measures per the published procedure (230 V / 50 Hz, 60 s
 settle, 5 readings averaged), writes lamps/<ID>/ into the comparison-data
-checkout, commits, and pushes. The website picks the lamp up automatically:
+checkout, commits, and pushes, then prints two ID labels (QR code linking to
+the lamp's page plus the ID, DK-11221 23x23 mm) on a Brother QL-820NWB network
+printer: one for the box, one for the lamp. Set HPCS_LABEL_PRINTER (e.g.
+tcp://192.168.1.50) or pass --printer; reprint anytime with
+`uv run label_printer.py <ID>`. The website picks the lamp up automatically:
 its device list is data-driven from the comparison-data bundles and the push
 triggers the auto-bump deploy. An .md page in the web repo is only ever needed
 for photos, where-to-buy links, or notes.

label_printer.py

@@ -0,0 +1,109 @@
+"""
+Lamp ID labels on the Brother QL-820NWB (DK-11221, 23x23 mm die-cut).
+
+Each label carries a QR code linking to the lamp's page on buildfor.life and
+the lamp ID as text. The station prints two per lamp: one for the box, one
+for the lamp itself.
+
+Printer address comes from --printer or the HPCS_LABEL_PRINTER environment
+variable, e.g. tcp://192.168.1.50 (the QL-820NWB listens on port 9100).
+
+Usage:
+    uv run label_printer.py L0006                     # print 2 labels
+    uv run label_printer.py L0006 --copies 1
+    uv run label_printer.py L0006 --preview out.png   # render only, no printer
+"""
+
+import argparse
+import os
+import sys
+
+import qrcode
+from PIL import Image, ImageDraw, ImageFont
+
+LABEL_ID = "23x23"  # DK-11221
+DOTS = (202, 202)  # printable area of the 23x23 label
+MODEL = "QL-820NWB"
+URL_BASE = "https://buildfor.life/comparisons/lamps/"
+TEXT_HEIGHT = 52  # bottom strip for the ID text
+
+
+def _font(size):
+    for name in ("arialbd.ttf", "arial.ttf", "DejaVuSans-Bold.ttf"):
+        try:
+            return ImageFont.truetype(name, size)
+        except OSError:
+            continue
+    return ImageFont.load_default(size)
+
+
+def render_label(lamp_id: str) -> Image.Image:
+    """202x202 1-bit label: QR to the lamp page on top, ID text below."""
+    image = Image.new("1", DOTS, 1)
+
+    qr = qrcode.QRCode(
+        error_correction=qrcode.constants.ERROR_CORRECT_M,
+        box_size=1,
+        border=2,  # quiet zone; tight but fine for close-range scanning
+    )
+    qr.add_data(f"{URL_BASE}{lamp_id.lower()}/")
+    qr.make(fit=True)
+    modules = len(qr.get_matrix())
+    qr_size = DOTS[1] - TEXT_HEIGHT
+    qr.box_size = max(1, qr_size // modules)
+    qr_img = qr.make_image().get_image().convert("1")
+    image.paste(qr_img, ((DOTS[0] - qr_img.width) // 2, (qr_size - qr_img.height) // 2))
+
+    draw = ImageDraw.Draw(image)
+    size = 44
+    while size > 10:
+        font = _font(size)
+        box = draw.textbbox((0, 0), lamp_id, font=font)
+        if box[2] - box[0] <= DOTS[0] - 8:
+            break
+        size -= 2
+    draw.text(
+        ((DOTS[0] - (box[2] - box[0])) // 2 - box[0], DOTS[1] - TEXT_HEIGHT + (TEXT_HEIGHT - (box[3] - box[1])) // 2 - box[1]),
+        lamp_id,
+        font=font,
+        fill=0,
+    )
+    return image
+
+
+def print_labels(lamp_id: str, printer: str, copies: int = 2) -> None:
+    """Render and send `copies` labels to the QL-820NWB."""
+    from brother_ql.backends.helpers import send
+    from brother_ql.conversion import convert
+    from brother_ql.raster import BrotherQLRaster
+
+    image = render_label(lamp_id)
+    raster = BrotherQLRaster(MODEL)
+    instructions = convert(qlr=raster, images=[image] * copies, label=LABEL_ID, cut=True)
+    send(instructions=instructions, printer_identifier=printer, backend_identifier="network", blocking=True)
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Print lamp ID labels (QR + ID)")
+    parser.add_argument("lamp_id", help="e.g. L0006")
+    parser.add_argument("--printer", default=os.environ.get("HPCS_LABEL_PRINTER", ""),
+                        help="tcp://<ip> of the QL-820NWB (default: HPCS_LABEL_PRINTER env)")
+    parser.add_argument("--copies", type=int, default=2)
+    parser.add_argument("--preview", metavar="PNG",
+                        help="Write the rendered label to a PNG instead of printing")
+    args = parser.parse_args()
+
+    lamp_id = args.lamp_id.upper()
+    if args.preview:
+        render_label(lamp_id).save(args.preview)
+        print(f"Wrote {args.preview}")
+        return
+    if not args.printer:
+        print("ERROR: no printer configured. Pass --printer tcp://<ip> or set HPCS_LABEL_PRINTER.")
+        sys.exit(1)
+    print_labels(lamp_id, args.printer, args.copies)
+    print(f"Printed {args.copies} label(s) for {lamp_id} on {args.printer}")
+
+
+if __name__ == "__main__":
+    main()

lamp_station.py

@@ -31,6 +31,10 @@ supports unbranded lamps without any barcode.
        website picks it up automatically (data-driven device list plus the
        auto-bump deploy); an .md page in the web repo is only ever needed
        for photos, where-to-buy links, or notes.
+    6. Two ID labels (QR to the lamp's page + the ID, DK-11221 23x23 mm)
+       print on the Brother QL-820NWB: one for the box, one for the lamp.
+       Configure the printer via HPCS_LABEL_PRINTER or --printer; reprint
+       any lamp later with `uv run label_printer.py L0006`.
 
 Usage:
     uv run lamp_station.py                      # defaults below
@@ -40,6 +44,7 @@ Usage:
 
 import argparse
 import json
+import os
 import re
 import subprocess
 import sys
@@ -304,6 +309,20 @@ def measure_one(new_id, ean, lamps, args, data_repo, existing_id=None):
     print("  The lamp publishes automatically (auto-bump deploy); add an .md under")
     print("  src/content/comparisons/lamps/ only for photos, buy links, or notes.")
 
+    # Two ID labels on the QL-820NWB: one for the box, one for the lamp.
+    if not args.no_labels:
+        if args.printer:
+            try:
+                from label_printer import print_labels
+                print_labels(lamp_id, args.printer, copies=2)
+                print(f"  Printed 2 ID labels for {lamp_id}.")
+            except Exception as e:  # noqa: BLE001 — a printer problem must not lose the run
+                print(f"  Label printing failed ({e}); reprint later with:")
+                print(f"    uv run label_printer.py {lamp_id}")
+        else:
+            print(f"  (no label printer configured; set HPCS_LABEL_PRINTER or use --printer,")
+            print(f"   reprint later with: uv run label_printer.py {lamp_id})")
+
 
 def main():
     parser = argparse.ArgumentParser(description="Barcode-driven lamp measurement station")
@@ -320,6 +339,11 @@ def main():
                         help="Write the bundle but skip git entirely")
     parser.add_argument("--no-push", action="store_true",
                         help="Commit locally but do not push")
+    parser.add_argument("--printer", default=os.environ.get("HPCS_LABEL_PRINTER", ""),
+                        help="QL-820NWB address, e.g. tcp://192.168.1.50 "
+                             "(default: HPCS_LABEL_PRINTER env)")
+    parser.add_argument("--no-labels", action="store_true",
+                        help="Skip printing the two ID labels after each lamp")
     args = parser.parse_args()
 
     data_repo = Path(args.data_repo)

pyproject.toml

@@ -7,4 +7,7 @@ requires-python = ">=3.11"
 dependencies = [
     "pyserial>=3.5",
     "colour-science>=0.4.4",
+    "qrcode>=8.2",
+    "pillow>=12.3.0",
+    "brother-ql-next>=0.12.0",
 ]