Add 313dpi continuous-tape rendering for the VC-500W
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"""
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Continuous-tape label rendering for the Brother VC-500W.
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Sheet labels (Avery etc.) are laid out in label_render.py as an HTML page.
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A tape printer is a different animal: one label at a time, fixed width, and
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the length is however long the content needs to be. So these are rendered as
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images at the printer's native resolution and sent to it over IPP.
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VC-500W facts this is built around:
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* 313 dpi, full colour, ZINK (no ink)
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* CZ tape in 9, 12, 19, 25 and 50mm widths
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* up to about 17 inches (431mm) per label
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* AirPrint, so it speaks IPP on port 631
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ORIENTATION: the tape feeds lengthwise, so the raster sent to the printer is
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normally rotated 90 degrees - the image is tape-width across and
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label-length tall. That is the default. If your first test print comes out
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sideways, untick "Rotate for tape feed" and print again; it is the one
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setting worth checking on a new printer.
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Created by: Jess Rogerson (yelling commands at Claude.AI)
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"""
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import io
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import logging
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import os
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from dataclasses import dataclass, field
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from typing import List, Optional
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from PIL import Image, ImageDraw, ImageFont
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logger = logging.getLogger(__name__)
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DPI = 313
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MAX_LENGTH_MM = 430.0
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MIN_LENGTH_MM = 12.0
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def mm_to_px(mm, dpi=DPI):
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return max(1, int(round(mm / 25.4 * dpi)))
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@dataclass
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class TapePreset:
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key: str
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name: str
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tape_mm: float
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printable_mm: float
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note: str = ''
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@property
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def printable_px(self):
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return mm_to_px(self.printable_mm)
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# Brother CZ tape widths. printable_mm leaves a hair of margin so a slightly
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# misaligned cassette doesn't clip the text; raise it toward tape_mm from
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# the settings page if you want true edge to edge.
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TAPE_PRESETS = {
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p.key: p for p in [
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TapePreset('cz9', 'CZ tape 9mm', 9.0, 8.0,
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'Tiny. One line, part number only.'),
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TapePreset('cz12', 'CZ tape 12mm', 12.0, 11.0,
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'One bold line, or two small ones.'),
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TapePreset('cz19', 'CZ tape 19mm', 19.0, 17.5,
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'Two comfortable lines. Good for bags.'),
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TapePreset('cz25', 'CZ tape 25mm', 25.0, 23.5,
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'The default roll. Image plus two lines.'),
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TapePreset('cz50', 'CZ tape 50mm', 50.0, 48.0,
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'Wide. Big artwork, drawer-front labels.'),
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]
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}
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DEFAULT_TAPE = 'cz25'
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FONT_CANDIDATES = {
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False: [ # regular
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'C:\\Windows\\Fonts\\segoeui.ttf',
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'C:\\Windows\\Fonts\\arial.ttf',
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'/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf',
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'/usr/share/fonts/truetype/liberation/LiberationSans-Regular.ttf',
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'/Library/Fonts/Arial.ttf',
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],
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True: [ # bold
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'C:\\Windows\\Fonts\\segoeuib.ttf',
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'C:\\Windows\\Fonts\\arialbd.ttf',
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'/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf',
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'/usr/share/fonts/truetype/liberation/LiberationSans-Bold.ttf',
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'/Library/Fonts/Arial Bold.ttf',
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],
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}
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_font_cache = {}
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def load_font(size_px, bold=False):
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"""Best available sans font at this pixel size. Never raises."""
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key = (int(size_px), bool(bold))
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if key in _font_cache:
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return _font_cache[key]
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for path in FONT_CANDIDATES[bool(bold)]:
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if os.path.exists(path):
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try:
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font = ImageFont.truetype(path, int(size_px))
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_font_cache[key] = font
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return font
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except Exception:
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continue
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# Pillow's built-in bitmap font: ugly at 313dpi but never fails.
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font = ImageFont.load_default()
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_font_cache[key] = font
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return font
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@dataclass
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class TapeOptions:
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tape: str = DEFAULT_TAPE
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fields: List[str] = field(default_factory=lambda: [
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'image', 'name', 'dimensions', 'part_number', 'accent'])
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rotate: bool = True
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copies: int = 1
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# Fixed length in mm, or None to size each label to its content.
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fixed_length_mm: Optional[float] = None
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padding_mm: float = 1.5
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font_scale: float = 1.0
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image_percent: int = 30
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align: str = 'left' # left | center
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outline: bool = False # hairline box, for checking alignment
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def get_tape(key):
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return TAPE_PRESETS.get(key or DEFAULT_TAPE, TAPE_PRESETS[DEFAULT_TAPE])
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def options_from_form(form):
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"""Build TapeOptions from request.form / request.args."""
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def number(key, default, cast=float):
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try:
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return cast(form.get(key, default))
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except (TypeError, ValueError):
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return default
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def flag(key, default=False):
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if key not in form:
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return default
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return str(form.get(key, '')).lower() in ('1', 'true', 'on', 'yes')
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fields = form.getlist('fields') if hasattr(form, 'getlist') else None
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length = (form.get('fixed_length_mm') or '').strip() if hasattr(form, 'get') else ''
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try:
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fixed = float(length) if length else None
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except ValueError:
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fixed = None
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return TapeOptions(
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tape=form.get('tape') or DEFAULT_TAPE,
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fields=fields if fields else ['image', 'name', 'dimensions',
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'part_number', 'accent'],
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rotate=flag('rotate', True),
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copies=max(1, min(99, number('copies', 1, int))),
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fixed_length_mm=fixed,
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padding_mm=max(0.0, min(10.0, number('padding_mm', 1.5))),
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font_scale=max(0.5, min(2.5, number('font_scale', 1.0))),
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image_percent=max(0, min(60, number('image_percent', 30, int))),
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align=form.get('align') or 'left',
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outline=flag('outline', False),
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)
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def _label_lines(label, fields):
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"""The text that goes on the tape, as (text, weight) pairs."""
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lines = []
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if 'name' in fields:
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title = (label.display_title if 'dimensions' in fields
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else label.name)
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if title:
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lines.append((title, 'title'))
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elif 'dimensions' in fields and label.dimensions:
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lines.append((label.dimensions, 'title'))
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if 'colour' in fields and label.colour_name:
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lines.append((label.colour_name, 'sub'))
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if 'category' in fields and label.category:
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lines.append((label.category.full_name, 'sub'))
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meta = []
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if 'part_number' in fields and label.part_number:
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meta.append(label.part_number)
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if 'alt_numbers' in fields and label.alt_part_numbers:
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meta.append(label.alt_part_numbers)
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if 'category_code' in fields and label.category and label.category.display_code:
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meta.append(label.category.display_code)
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if meta:
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lines.append((' \u00b7 '.join(meta), 'meta'))
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if 'location' in fields and label.location:
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lines.append((label.location, 'meta'))
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return lines
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def _text_width(draw, text, font):
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try:
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box = draw.textbbox((0, 0), text, font=font)
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return box[2] - box[0]
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except Exception:
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return draw.textlength(text, font=font)
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def render_label(label, options, upload_folder):
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"""
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Render one PartLabel as a PIL image, unrotated (reading left to right).
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Height is the printable tape width; width is the label length.
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"""
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tape = get_tape(options.tape)
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height = tape.printable_px
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padding = mm_to_px(options.padding_mm)
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fields = set(options.fields)
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lines = _label_lines(label, fields)
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# Type sizes scale off tape width so 9mm doesn't get 25mm's typography.
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base = height * 0.34 * options.font_scale
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if len(lines) > 2:
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base *= 0.78
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sizes = {
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'title': max(8, int(base)),
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'sub': max(7, int(base * 0.72)),
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'meta': max(6, int(base * 0.62)),
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}
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fonts = {
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'title': load_font(sizes['title'], bold=True),
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'sub': load_font(sizes['sub'], bold=False),
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'meta': load_font(sizes['meta'], bold=False),
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}
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# Artwork
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art = None
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art_width = 0
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if 'image' in fields and label.image and options.image_percent:
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path = os.path.join(upload_folder, label.image.replace('/', os.sep))
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if os.path.exists(path):
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try:
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art = Image.open(path).convert('RGBA')
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box = height - 2 * padding
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art.thumbnail((box, box), Image.LANCZOS)
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art_width = art.width + padding
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except Exception as exc:
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logger.warning('Could not load part image %s: %s', path, exc)
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art = None
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accent_width = mm_to_px(1.2) if ('accent' in fields and label.category) else 0
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# Measure to find the natural length
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probe = ImageDraw.Draw(Image.new('RGB', (10, 10)))
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text_width = 0
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for text, weight in lines:
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text_width = max(text_width, _text_width(probe, text, fonts[weight]))
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natural = accent_width + padding + art_width + text_width + 2 * padding
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if options.fixed_length_mm:
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width = mm_to_px(min(MAX_LENGTH_MM, max(MIN_LENGTH_MM,
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options.fixed_length_mm)))
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else:
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width = max(mm_to_px(MIN_LENGTH_MM),
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min(mm_to_px(MAX_LENGTH_MM), int(natural)))
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canvas = Image.new('RGB', (width, height), 'white')
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draw = ImageDraw.Draw(canvas)
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if options.outline:
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draw.rectangle([0, 0, width - 1, height - 1], outline=(190, 190, 190),
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width=max(1, mm_to_px(0.2)))
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cursor_x = 0
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if accent_width:
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colour = label.category.accent_colour()
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try:
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rgb = tuple(int(colour.lstrip('#')[i:i + 2], 16) for i in (0, 2, 4))
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except Exception:
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rgb = (209, 16, 19)
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draw.rectangle([0, 0, accent_width, height], fill=rgb)
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cursor_x = accent_width + padding
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if art is not None:
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canvas.paste(art, (cursor_x, (height - art.height) // 2), art)
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cursor_x += art.width + padding
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# Vertically centre the text block
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total_text = sum(sizes[w] * 1.22 for _, w in lines)
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y = max(padding, (height - total_text) / 2)
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available = width - cursor_x - padding
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for text, weight in lines:
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font = fonts[weight]
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shown = text
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while (_text_width(draw, shown, font) > available and len(shown) > 2):
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shown = shown[:-2]
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if shown != text and len(shown) > 1:
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shown = shown[:-1] + '\u2026'
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x = cursor_x
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if options.align == 'center':
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x = cursor_x + max(0, (available - _text_width(draw, shown, font)) / 2)
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draw.text((x, y), shown, font=font, fill=(0, 0, 0))
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y += sizes[weight] * 1.22
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if options.rotate:
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canvas = canvas.rotate(90, expand=True)
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return canvas
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def image_to_bytes(image, mime_type):
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"""Serialise a rendered label in whatever format the printer accepts."""
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buffer = io.BytesIO()
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if mime_type == 'image/jpeg':
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image.convert('RGB').save(buffer, 'JPEG', quality=95, dpi=(DPI, DPI))
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elif mime_type == 'image/png':
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image.save(buffer, 'PNG', dpi=(DPI, DPI))
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elif mime_type == 'application/pdf':
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image.convert('RGB').save(buffer, 'PDF', resolution=DPI)
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else:
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raise ValueError(f'Cannot produce {mime_type}')
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buffer.seek(0)
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return buffer.getvalue()
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def render_batch_pdf(labels, options, upload_folder):
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"""All selected labels as one multi-page PDF, one tape label per page."""
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images = []
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for label in labels:
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for _ in range(options.copies):
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images.append(render_label(label, options, upload_folder)
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.convert('RGB'))
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if not images:
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return None
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buffer = io.BytesIO()
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images[0].save(buffer, 'PDF', resolution=DPI, save_all=True,
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append_images=images[1:])
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buffer.seek(0)
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return buffer
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def preview_png(label, options, upload_folder, scale=2.0):
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"""
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A screen-sized preview. Rendered unrotated however the print option is
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set, because a sideways preview is useless to look at.
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"""
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saved = options.rotate
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options.rotate = False
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try:
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image = render_label(label, options, upload_folder)
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finally:
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options.rotate = saved
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target_height = int(get_tape(options.tape).printable_mm * scale * 4)
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ratio = target_height / image.height
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image = image.resize((max(1, int(image.width * ratio)), target_height),
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Image.LANCZOS)
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buffer = io.BytesIO()
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image.save(buffer, 'PNG')
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buffer.seek(0)
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return buffer
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