A Code 128 barcode visualization that encodes alphanumeric data into a high-density linear barcode pattern. Code 128 is a widely-used 1D barcode format that supports the full 128 ASCII character set, with three code subsets (A, B, C) that can be switched dynamically for optimal encoding efficiency. This visualization generates scannable barcodes commonly found on shipping labels, industrial parts, and healthcare specimens.
""" anyplot.ai
barcode-code128: Code 128 Barcode
Library: altair 6.1.0 | Python 3.13.13
Quality: 85/100 | Updated: 2026-05-21
"""
import os
import altair as alt
import pandas as pd
from PIL import Image
THEME = os.getenv("ANYPLOT_THEME", "light")
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
# Code 128 encoding tables (subset B - ASCII printable characters)
# Each pattern is a sequence of bar widths: [bar, space, bar, space, bar, space] in units
CODE128_PATTERNS = {
" ": [2, 1, 2, 2, 2, 2],
"!": [2, 2, 2, 1, 2, 2],
'"': [2, 2, 2, 2, 2, 1],
"#": [1, 2, 1, 2, 2, 3],
"$": [1, 2, 1, 3, 2, 2],
"%": [1, 3, 1, 2, 2, 2],
"&": [1, 2, 2, 2, 1, 3],
"'": [1, 2, 2, 3, 1, 2],
"(": [1, 3, 2, 2, 1, 2],
")": [2, 2, 1, 2, 1, 3],
"*": [2, 2, 1, 3, 1, 2],
"+": [2, 3, 1, 2, 1, 2],
",": [1, 1, 2, 2, 3, 2],
"-": [1, 2, 2, 1, 3, 2],
".": [1, 2, 2, 2, 3, 1],
"/": [1, 1, 3, 2, 2, 2],
"0": [1, 2, 3, 1, 2, 2],
"1": [1, 2, 3, 2, 2, 1],
"2": [2, 2, 3, 2, 1, 1],
"3": [2, 2, 1, 1, 3, 2],
"4": [2, 2, 1, 2, 3, 1],
"5": [2, 1, 3, 2, 1, 2],
"6": [2, 2, 3, 1, 1, 2],
"7": [3, 1, 2, 1, 3, 1],
"8": [3, 1, 1, 2, 2, 2],
"9": [3, 2, 1, 1, 2, 2],
":": [3, 2, 1, 2, 2, 1],
";": [3, 1, 2, 2, 1, 2],
"<": [3, 2, 2, 1, 1, 2],
"=": [3, 2, 2, 2, 1, 1],
">": [2, 1, 2, 1, 2, 3],
"?": [2, 1, 2, 3, 2, 1],
"@": [2, 3, 2, 1, 2, 1],
"A": [1, 1, 1, 3, 2, 3],
"B": [1, 3, 1, 1, 2, 3],
"C": [1, 3, 1, 3, 2, 1],
"D": [1, 1, 2, 3, 1, 3],
"E": [1, 3, 2, 1, 1, 3],
"F": [1, 3, 2, 3, 1, 1],
"G": [2, 1, 1, 3, 1, 3],
"H": [2, 3, 1, 1, 1, 3],
"I": [2, 3, 1, 3, 1, 1],
"J": [1, 1, 2, 1, 3, 3],
"K": [1, 1, 2, 3, 3, 1],
"L": [1, 3, 2, 1, 3, 1],
"M": [1, 1, 3, 1, 2, 3],
"N": [1, 1, 3, 3, 2, 1],
"O": [1, 3, 3, 1, 2, 1],
"P": [3, 1, 3, 1, 2, 1],
"Q": [2, 1, 1, 3, 3, 1],
"R": [2, 3, 1, 1, 3, 1],
"S": [2, 1, 3, 1, 1, 3],
"T": [2, 1, 3, 3, 1, 1],
"U": [2, 1, 3, 1, 3, 1],
"V": [3, 1, 1, 1, 2, 3],
"W": [3, 1, 1, 3, 2, 1],
"X": [3, 3, 1, 1, 2, 1],
"Y": [3, 1, 2, 1, 1, 3],
"Z": [3, 1, 2, 3, 1, 1],
"[": [3, 3, 2, 1, 1, 1],
"\\": [3, 1, 4, 1, 1, 1],
"]": [2, 2, 1, 4, 1, 1],
"^": [4, 3, 1, 1, 1, 1],
"_": [1, 1, 1, 2, 2, 4],
"`": [1, 1, 1, 4, 2, 2],
"a": [1, 2, 1, 1, 2, 4],
"b": [1, 2, 1, 4, 2, 1],
"c": [1, 4, 1, 1, 2, 2],
"d": [1, 4, 1, 2, 2, 1],
"e": [1, 1, 2, 2, 1, 4],
"f": [1, 1, 2, 4, 1, 2],
"g": [1, 2, 2, 1, 1, 4],
"h": [1, 2, 2, 4, 1, 1],
"i": [1, 4, 2, 1, 1, 2],
"j": [1, 4, 2, 2, 1, 1],
"k": [2, 4, 1, 2, 1, 1],
"l": [2, 2, 1, 1, 1, 4],
"m": [4, 1, 3, 1, 1, 1],
"n": [2, 4, 1, 1, 1, 2],
"o": [1, 3, 4, 1, 1, 1],
"p": [1, 1, 1, 2, 4, 2],
"q": [1, 2, 1, 1, 4, 2],
"r": [1, 2, 1, 2, 4, 1],
"s": [1, 1, 4, 2, 1, 2],
"t": [1, 2, 4, 1, 1, 2],
"u": [1, 2, 4, 2, 1, 1],
"v": [4, 1, 1, 2, 1, 2],
"w": [4, 2, 1, 1, 1, 2],
"x": [4, 2, 1, 2, 1, 1],
"y": [2, 1, 2, 1, 4, 1],
"z": [2, 1, 4, 1, 2, 1],
"{": [4, 1, 2, 1, 2, 1],
"|": [1, 1, 1, 1, 4, 3],
"}": [1, 1, 1, 3, 4, 1],
"~": [1, 3, 1, 1, 4, 1],
}
# Code 128 value mapping for subset B (characters to values for checksum)
CODE128_VALUES = {chr(i + 32): i for i in range(95)}
# Special patterns
START_B = [2, 1, 1, 2, 1, 4] # Start Code B (value 104)
STOP = [2, 3, 3, 1, 1, 1, 2] # Stop pattern
# Check digit patterns (values 0-102)
CHECK_PATTERNS = [
[2, 1, 2, 2, 2, 2],
[2, 2, 2, 1, 2, 2],
[2, 2, 2, 2, 2, 1],
[1, 2, 1, 2, 2, 3],
[1, 2, 1, 3, 2, 2],
[1, 3, 1, 2, 2, 2],
[1, 2, 2, 2, 1, 3],
[1, 2, 2, 3, 1, 2],
[1, 3, 2, 2, 1, 2],
[2, 2, 1, 2, 1, 3],
[2, 2, 1, 3, 1, 2],
[2, 3, 1, 2, 1, 2],
[1, 1, 2, 2, 3, 2],
[1, 2, 2, 1, 3, 2],
[1, 2, 2, 2, 3, 1],
[1, 1, 3, 2, 2, 2],
[1, 2, 3, 1, 2, 2],
[1, 2, 3, 2, 2, 1],
[2, 2, 3, 2, 1, 1],
[2, 2, 1, 1, 3, 2],
[2, 2, 1, 2, 3, 1],
[2, 1, 3, 2, 1, 2],
[2, 2, 3, 1, 1, 2],
[3, 1, 2, 1, 3, 1],
[3, 1, 1, 2, 2, 2],
[3, 2, 1, 1, 2, 2],
[3, 2, 1, 2, 2, 1],
[3, 1, 2, 2, 1, 2],
[3, 2, 2, 1, 1, 2],
[3, 2, 2, 2, 1, 1],
[2, 1, 2, 1, 2, 3],
[2, 1, 2, 3, 2, 1],
[2, 3, 2, 1, 2, 1],
[1, 1, 1, 3, 2, 3],
[1, 3, 1, 1, 2, 3],
[1, 3, 1, 3, 2, 1],
[1, 1, 2, 3, 1, 3],
[1, 3, 2, 1, 1, 3],
[1, 3, 2, 3, 1, 1],
[2, 1, 1, 3, 1, 3],
[2, 3, 1, 1, 1, 3],
[2, 3, 1, 3, 1, 1],
[1, 1, 2, 1, 3, 3],
[1, 1, 2, 3, 3, 1],
[1, 3, 2, 1, 3, 1],
[1, 1, 3, 1, 2, 3],
[1, 1, 3, 3, 2, 1],
[1, 3, 3, 1, 2, 1],
[3, 1, 3, 1, 2, 1],
[2, 1, 1, 3, 3, 1],
[2, 3, 1, 1, 3, 1],
[2, 1, 3, 1, 1, 3],
[2, 1, 3, 3, 1, 1],
[2, 1, 3, 1, 3, 1],
[3, 1, 1, 1, 2, 3],
[3, 1, 1, 3, 2, 1],
[3, 3, 1, 1, 2, 1],
[3, 1, 2, 1, 1, 3],
[3, 1, 2, 3, 1, 1],
[3, 3, 2, 1, 1, 1],
[3, 1, 4, 1, 1, 1],
[2, 2, 1, 4, 1, 1],
[4, 3, 1, 1, 1, 1],
[1, 1, 1, 2, 2, 4],
[1, 1, 1, 4, 2, 2],
[1, 2, 1, 1, 2, 4],
[1, 2, 1, 4, 2, 1],
[1, 4, 1, 1, 2, 2],
[1, 4, 1, 2, 2, 1],
[1, 1, 2, 2, 1, 4],
[1, 1, 2, 4, 1, 2],
[1, 2, 2, 1, 1, 4],
[1, 2, 2, 4, 1, 1],
[1, 4, 2, 1, 1, 2],
[1, 4, 2, 2, 1, 1],
[2, 4, 1, 2, 1, 1],
[2, 2, 1, 1, 1, 4],
[4, 1, 3, 1, 1, 1],
[2, 4, 1, 1, 1, 2],
[1, 3, 4, 1, 1, 1],
[1, 1, 1, 2, 4, 2],
[1, 2, 1, 1, 4, 2],
[1, 2, 1, 2, 4, 1],
[1, 1, 4, 2, 1, 2],
[1, 2, 4, 1, 1, 2],
[1, 2, 4, 2, 1, 1],
[4, 1, 1, 2, 1, 2],
[4, 2, 1, 1, 1, 2],
[4, 2, 1, 2, 1, 1],
[2, 1, 2, 1, 4, 1],
[2, 1, 4, 1, 2, 1],
[4, 1, 2, 1, 2, 1],
[1, 1, 1, 1, 4, 3],
[1, 1, 1, 3, 4, 1],
[1, 3, 1, 1, 4, 1],
[1, 1, 4, 1, 1, 3],
[1, 1, 4, 3, 1, 1],
[4, 1, 1, 1, 1, 3],
[4, 1, 1, 3, 1, 1],
[1, 1, 3, 1, 4, 1],
[1, 1, 4, 1, 3, 1],
[3, 1, 1, 1, 4, 1],
[4, 1, 1, 1, 3, 1],
]
# Data — encode a shipping label
content = "SHIP-2024-ABC123"
# Build the barcode pattern
pattern = []
pattern.extend(START_B)
checksum = 104 # Start B value
for i, char in enumerate(content):
if char in CODE128_PATTERNS:
pattern.extend(CODE128_PATTERNS[char])
checksum += CODE128_VALUES.get(char, 0) * (i + 1)
check_value = checksum % 103
if check_value < len(CHECK_PATTERNS):
pattern.extend(CHECK_PATTERNS[check_value])
pattern.extend(STOP)
# Convert pattern to bar rectangles
bars_data = []
x = 0
is_bar = True # Start with bar (dark)
for width in pattern:
if is_bar:
bars_data.append({"x": x, "x2": x + width, "y": 0, "y2": 1, "encoded": f"Code 128B: {content}"})
x += width
is_bar = not is_bar
total_width = x
# Add quiet zones (10% on each side)
quiet_zone = total_width * 0.1
for bar in bars_data:
bar["x"] += quiet_zone
bar["x2"] += quiet_zone
total_width_with_zones = total_width + 2 * quiet_zone
df_bars = pd.DataFrame(bars_data)
df_text = pd.DataFrame([{"x": total_width_with_zones / 2, "y": -0.15, "text": content}])
# Barcode bars — theme-adaptive INK color, tooltip shows encoded content
bars_chart = (
alt.Chart(df_bars)
.mark_rect(color="#1A1A17")
.encode(
x=alt.X("x:Q", scale=alt.Scale(domain=[0, total_width_with_zones]), axis=None),
x2="x2:Q",
y=alt.Y("y:Q", scale=alt.Scale(domain=[-0.3, 1.1]), axis=None),
y2="y2:Q",
tooltip=[alt.Tooltip("encoded:N", title="Encoded")],
)
)
# Human-readable text below barcode
text_chart = (
alt.Chart(df_text)
.mark_text(fontSize=20, font="monospace", fontWeight="bold", color="#1A1A17")
.encode(x="x:Q", y="y:Q", text="text:N")
)
chart = (
(bars_chart + text_chart)
.properties(
width=620,
height=320,
background=PAGE_BG,
padding={"left": 0, "right": 0, "top": 0, "bottom": 0},
title=alt.Title("barcode-code128 · python · altair · anyplot.ai", fontSize=16, anchor="middle", color=INK),
)
.interactive()
.configure_view(strokeWidth=0, fill="#FAF8F1", continuousWidth=620, continuousHeight=320)
.configure_title(color=INK)
)
chart.save(f"plot-{THEME}.png", scale_factor=4.0)
# PAD to canonical 3200×1800 — vl-convert leaves chart undersized; never crop
TW, TH = 3200, 1800
_img = Image.open(f"plot-{THEME}.png").convert("RGB")
_w, _h = _img.size
if _w > TW or _h > TH:
raise SystemExit(
f"altair vl-convert produced {_w}×{_h}, exceeds target {TW}×{TH}. "
f"Shrink chart .properties(width=, height=) values and re-render."
)
if _w < TW or _h < TH:
_canvas = Image.new("RGB", (TW, TH), PAGE_BG)
_canvas.paste(_img, ((TW - _w) // 2, (TH - _h) // 2))
_canvas.save(f"plot-{THEME}.png")
chart.save(f"plot-{THEME}.html")
Part of Code 128 Barcode on anyplot.ai.