PostBar (Canada Post CPC four-state)

PostBar is Canada Post Corporation's (CPC) name for its four-state, height-coded bar code family. Unlike the rest of this SDK's postal family (POSTNET, PLANET, RM4SCC, KIX, Australia Post, Japan Post, IMb), a PostBar symbol's payload is protected by a real Reed-Solomon code, not a simple check character.

Canada Post's own engineering specification for PostBar is not published — it is available only on request from Canada Post. This SDK does not hold or rely on that document. Instead, it implements PostBar from the complete technical disclosure in US Patent 5,602,382A ("Multiple Bar Code Processing," Canada Post Corporation, filed 1994, expired around 2014), verified directly against the patent's own fully worked examples — see licenses/postbar.license for the full provenance record, including why an earlier automated read of the same patent produced unreliable results and how that was resolved.

Supported profiles

Format	Runtime id	Application	Total bars	Reed-Solomon
PostBar.C10	postbarc10	Canada Post internal machines	56	(16,6) over GF(64)
PostBar.D22	postbard22	Customer-applied, domestic (Canada)	79	(25,21) over GF(64)
PostBar.G12	postbarg12	International / global	49	(15,11) over GF(64)

The patent also names PostBar.D07, D12, G22, S06, S11 and S21, but this SDK implements only the three profiles above — the ones whose full field layouts and (for C10 and D22) worked numerical examples were directly verified against the patent. Extending to another named profile would need the same treatment, not an assumption that the pattern generalizes.

All three are reported as canWrite: true and canRead: true by listFormats() and are part of the counted format registry — unlike KarTrak ACI, PostBar renders as an ordinary monochrome BitMatrix (height-coded bars, the same visual language as the rest of the postal family), so it fits the standard encode()/decode() contract directly.

Writing

import { encodePostBarC10, encodePostBarD22, encodePostBarG12 } from '@sythos/js_barcode_universal/oned';

// PostBar.C10: a 6-character ANANAN postal code and a 4-digit quaternary
// (0-3) machine ID. This is the patent's own worked example.
const c10 = encodePostBarC10({ postalCode: 'K1S5B6', machineId: '2010' });

// PostBar.D22: postal code, a 4-character address locator and an
// 11-character customer information field (both from the alphanumeric
// alphabet: space, A-Z, 0-9).
const d22 = encodePostBarD22({
  postalCode: 'L3B4T9',
  addressLocator: '1420',
  customerInfo: 'CFFMIPLXF6V',
});

// PostBar.G12: a 3-digit country code and an 8-character postal code (no
// letter/digit grammar for this profile -- pad with spaces as needed).
const g12 = encodePostBarG12({ countryCode: '180', postalCode: '91266   ' });

The root dispatcher accepts the same profile ids and field objects as value:

import { encode, toImageData } from '@sythos/js_barcode_universal';

const matrix = encode({ postalCode: 'K1S5B6', machineId: '2010' }, { format: 'postbarc10' });
const image = toImageData(matrix, { scale: 4, margin: 24, barHeight: 60 });

A postal code may include the conventional space (K1S 5B6); it is stripped before validation. addressLocator and customerInfo accept any combination of space, A-Z and 0-9 (Table 2 of the patent); the postal-code positions in C10/D22 strictly alternate letter/digit (A-N-A-N-A-N).

Reading images

import { decode, toImageData } from '@sythos/js_barcode_universal';

const image = toImageData(encodePostBarC10({ postalCode: 'K1S5B6', machineId: '2010' }), {
  scale: 4, margin: 24, barHeight: 60,
});

const [result] = decode(image, { formats: ['postbarc10'] });
console.log(result?.postalCode, result?.machineId, result?.corrections);
// K1S5B6 2010 0

Every result includes corrections: the number of Reed-Solomon symbol errors actually corrected (0 for a clean read). Damage within the format's correction capacity (2t+e <= 2*checkSymbols, see the patent) is repaired silently; damage beyond it returns no result rather than plausible-looking wrong data — this SDK's Reed-Solomon decoder verifies every correction against the syndromes before accepting it.

For camera capture, opt into the stricter profile:

const hits = decode(cameraFrame, { formats: ['postbarc10'], profile: 'camera' });

The camera profile requires a measurable quiet zone on both sides of the bars, the same requirement as the rest of the postal family. PostBar decoding does not promise arbitrary projective distortion, curved media, severe glare or multiple overlapping symbols.

Verification and licensing boundary

The 'A'/'N'/'Z' symbol tables and field layouts are original Sythos data, transcribed directly from the patent's rendered page images (not any automated OCR/text extraction, which was found to garble them) and independently verified by reproducing the patent's own fully worked PostBar.C10 example — DCI=Z, postal code K1S 5B6, machine ID DHAH — exactly, symbol for symbol, plus PostBar.D22's own worked example. Reed-Solomon arithmetic reuses this SDK's existing, already-shipped GaloisField/Reed-Solomon primitives (the same GF(64) constant used elsewhere in this SDK), not a second implementation. No source code, table or image asset from any other barcode implementation is copied or shipped; none is known to publicly implement PostBar (BWIPP, Zint and ZXing were checked). See licenses/postbar.license and NOTICE.md. This implementation is not certified, endorsed or reviewed by Canada Post.