rubar

A Rust library for barcode encoding and rendering with Python bindings.

Why rubar?

Most barcode libraries make decisions for you: automatic encoding selection, implicit quiet zones, magic checksum handling. This is convenient until you need precise control—especially for GS1-128 barcodes where FNC1 placement matters, or when you need exact geometry for document layout.

rubar takes a different approach:

• Exact geometry — You get module-level bar positions, not opaque images
• Explicit control — FNC1, code set selection, quiet zones are all explicit parameters
• Zero magic — No automatic anything; you specify exactly what you want

What rubar does NOT do

• Layout — No text labels, no human-readable digits below barcodes
• Decoding — Encoding only; use a scanner library for reading
• Implicit quiet zones — Add them explicitly if you need them

Installation

pip install rubar

Usage

Code 128

from rubar import Code128, Data

barcode = Code128([Data("HELLO-123")])

# Get the geometry (module positions)
geom = barcode.geometry()
print(f"Total width: {geom.total_modules} modules")
print(f"Number of bars: {len(geom.bars)}")

# Render to SVG (unitless, scales to any size)
svg = barcode.render_svg()

# Render to PNG (exact pixel dimensions)
png = barcode.render_png(400, 100, unit="px")

Code sets are chosen to minimise the symbol count. Digit runs pack two-per-symbol into Code Set C, so Data("12345678901234") is 7 symbols rather than 14 — which matters because a barcode is normally sized from its symbol count.

GS1-128 with FNC1

GS1-128 barcodes require FNC1 immediately after the start symbol. With rubar, this is explicit:

from rubar import Code128, Data, FNC1

# GS1-128: Application Identifier (01) + GTIN-14
barcode = Code128([
    FNC1(),             # FNC1 indicates GS1 format
    Data("01"),         # AI: GTIN
    Data("12345678901234"),
])

svg = barcode.render_svg()

Planning spans the whole symbol list, so a digit run split across several Data entries still packs as one run.

A StartA(), StartB() or StartC() symbol pins the initial code set and planning continues from there. It is rarely needed — the planner already picks Code Set C for numeric payloads like the one above.

QR Code

from rubar import QrCode

qr = QrCode("https://example.com")

# QR geometry is a 2D module grid
geom = qr.geometry()
print(f"QR size: {geom.size}x{geom.size} modules")

svg = qr.render_svg()
png = qr.render_png(200, 200, unit="px")

Other Symbologies

from rubar import Code39, UpcA, Ean8, Itf

code39 = Code39("HELLO")
upc = UpcA("012345678905")      # 12 digits with check digit
ean8 = Ean8("12345670")         # 8 digits with check digit
itf14 = Itf("00012345678905")   # Even-length numeric

Rendering

SVG: Pure Geometry

render_svg() produces a scalable SVG with only a viewBox—no width or height attributes. The viewBox uses module coordinates, so a 95-module barcode has viewBox="0 0 95 1".

svg = barcode.render_svg()
# Embed in HTML/CSS and control size there

PNG: Exact Pixels

render_png() requires explicit dimensions. Three unit modes:

# Pixels (direct)
png = barcode.render_png(400, 100, unit="px")

# Inches (requires dpi)
png = barcode.render_png(2.0, 0.5, unit="in", dpi=300)

# Millimeters (requires dpi)
png = barcode.render_png(50.0, 12.0, unit="mm", dpi=300)

Quiet Zones

Quiet zones (empty space around the barcode) are not added by default. Add them explicitly:

svg = barcode.render_svg(quiet_zone_modules=10)
png = barcode.render_png(400, 100, unit="px", quiet_zone_modules=10)

Integration with rupdf

rubar is the barcode engine for rupdf, a PDF generation library. While designed for that integration, rubar is fully usable as a standalone library for any barcode generation needs.

Supported Symbologies

License

MIT