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 struct barcode.Symbol {
    kind as string,                    # "matrix" (2D) or "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
};

barcode.defaults() gives scale 4, quiet 4, EC level M, black on white.

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, byte-mode codewords, and 1D bar patterns; 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 1-10 (up to ~270 bytes at level L). Byte mode only (universal); numeric / alphanumeric compaction and versions 11-40 are follow-ons.
• The GF(256) / Reed-Solomon math lives in a private barcode_ecc.j (included), isolated so it can be extracted into an ecc module if a second consumer (e.g. Data Matrix) ever appears.
• No general image library - the only raster need is a monochrome bitmap, which the PNG encoder covers directly.
• Data Matrix / Aztec / PDF417 are not included (a Data Matrix would reuse barcode_ecc.j inside this module).

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.