#barcode - barcode / QR code generation

Import with import "barcode.j" as barcode;. Generate scannable codes as images - the complement to label, which emits printer-native barcode commands. encode(data, symbology, opts) builds a device-independent Symbol (a module matrix for 2D, bar widths for 1D), and the renderers turn it into SVG, PNG, terminal art, or the raw matrix. Pure .j over compress (zlib)

• crc (CRC-32) + encoding + the bitwise operators - no image library; runs

on both binaries.

import "barcode.j" as barcode;

def opts as barcode.Options init barcode.defaults();
def qr as barcode.Symbol init barcode.encode("https://example.com", "qr", $opts);
def svg as string init barcode.svg($qr, $opts);   # embed in HTML / email
def png as bytes init barcode.png($qr, $opts);     # a monochrome PNG

Runnable: examples/modules/barcode_demo.j.

#Encoding

barcode.encode(data, symbology, opts) -> Symbol. Symbologies:

def enum barcode.SymbolKind { Matrix, Linear };
def struct barcode.Symbol {
    kind as SymbolKind,                # SymbolKind.Matrix (2D) or SymbolKind.Linear (1D)
    size as int,                       # matrix dimension (2D; 0 for 1D)
    matrix as list of list of bool,    # the 2D module grid (true = dark)
    bars as list of int,               # 1D bar/space run widths, starting with a bar
    text as string                     # the encoded data
};

#Rendering

def struct barcode.Options {
    scale as int, height as int, quiet as int,
    ecLevel as string, foreground as string, background as string,
    humanReadable as bool   # render the data as a text line under a 1D SVG (on by default)
};

barcode.defaults() gives scale 8, quiet 4, EC level M, black on white, and a human-readable text line under 1D SVGs (opts.humanReadable = false to omit it). Scale 8 (8 px per module) keeps a code comfortably scannable by a phone camera off a screen - a smaller render can defeat autofocus or pick up screen moire; lower opts.scale for a more compact image.

opts.scale is pixels (PNG) or units (SVG) per module / narrow bar; opts.quiet is the mandatory light border in modules; opts.height is the bar height for 1D codes; opts.foreground / background are the SVG / PNG colours.

#Verification

Correctness is pinned two ways: the overlay (modules/barcode_test.j) checks the Reed-Solomon against the canonical QR vector, the format / version BCH against known values, mode codewords (including the QR spec's numeric worked example), the DataMatrix 10x10 matrix against zint, and 1D bar patterns against independent reference encoders; and the Go suite (cmd/jennifer/barcode_test.go) renders PNGs, decodes them with the standard library (proving the hand-rolled PNG is byte-correct), and - where zbarimg is available - optically scans them to confirm they read.

#Scope

• QR versions 1-40, all four EC levels, with numeric / alphanumeric / byte mode chosen for compactness. A byte-mode payload with non-ASCII bytes gets an ECI(26) UTF-8 declaration, so it decodes as UTF-8 in a strict reader. Kanji mode, other ECI assignments, and structured-append are not covered. Large versions (v30+) are slow to render (the mask-penalty scoring runs in the tree-walking interpreter), not incorrect.
• DataMatrix ECC200 square symbols 10x10 to 26x26 (single data region), ASCII encodation. Rectangular symbols, larger sizes (region interleaving), and the C40 / Text / X12 / EDIFACT / Base256 encodations are follow-ons; a letter-heavy payload is valid but larger than an optimal-encodation encoder would produce.
• The GF(256) / Reed-Solomon math lives in a private barcode_ecc.inc.j (included, parameterised by primitive polynomial and generator base, so QR (0x11d) and DataMatrix (0x12d) share it).
• No general image library - the only raster need is a monochrome bitmap, which the PNG encoder covers directly.
• Aztec / PDF417 / MaxiCode are not included.

#See also

• label.md - printer-native barcode commands (the other half).
• compress.md / crc.md - the PNG encoder's zlib and CRC-32.
• modules/index.md - the module catalog and import rules.