FAILURE MAP
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FA-79761 / Barcode symbology encoding / Open access

Narrow bars disappear after width reduction · case 01

At low resolutions single-module bars vanish, making the symbol unreadable.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Bars reduced to zero width are kept at zero instead of being clamped to one pixel.

THE FAILURE

Bars reduced to zero width are kept at zero instead of being clamped to one pixel.

Unsuccessful approach: Clamping only negative widths still allows zero-width bars.

Case contract

Render a module string ("1" bar, "0" space) at xn/xd device pixels per module after `quiet` leading quiet-zone modules. Module boundary k lies at round-half-up((quiet + k) * X), computed from the exact fraction so errors do not accumulate. Adjacent bar modules merge into one bar [start, end); bar width reduction shaves `bwr` pixels from the right edge of each bar, but a bar is never narrower than 1 pixel.

Why this case matters

Retail, logistics, pharmacy and document workflows depend on encoders that produce exactly the module pattern, code-set switches, separators and quiet zones scanners expect; one misplaced module or separator makes a label unreadable or, worse, scan as different data.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(mods, xn, xd, bwr, quiet):
    X = Fraction(xn, xd)
    def edge(i):
        return math.floor((quiet + i) * X + Fraction(1, 2))
    bars = []
    i = 0
    n = len(mods)
    while i < n:
        if mods[i] == '1':
            j = i
            while j < n and mods[j] == '1':
                j += 1
            s, e = edge(i), edge(j) - bwr
            if e - s < 0:
                e = s
            bars.append([s, e])
            i = j
        else:
            i += 1
    return bars
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[('010111110', 11, 5, 2, 0), [[2, 3], [7, 16]]], [('1100111001', 1, 1, 1, 10), [[10, 11], [14, 16], [19, 20]]], [('0001111', 2, 1, 0, 1), [[8, 16]]], [('011', 5, 2, 1, 10), [[28, 32]]], [('00001010', 1, 1, 0, 1), [[5, 6], [7, 8]]], [('101100101', 11, 5, 0, 0), [[0, 2], [4, 9], [13, 15], [18, 20]]], [('00101', 3, 1, 0, 0), [[6, 9], [12, 15]]], [('11000100', 4, 3, 2, 1), [[1, 2], [8, 9]]]], [[('1', 4, 3, 1, 0), [[0, 1]]], [('00010000011', 11, 5, 2, 10), [[29, 30], [42, 44]]], [('0010101000110', 7, 3, 0, 0), [[5, 7], [9, 12], [14, 16], [23, 28]]], [('1111', 9, 4, 2, 3), [[7, 14]]], [('1100001111', 9, 4, 0, 0), [[0, 5], [14, 23]]], [('000010010001', 9, 4, 1, 0), [[9, 10], [16, 17], [25, 26]]], [('0011000', 3, 1, 2, 3), [[15, 19]]], [('10000111', 9, 4, 2, 3), [[7, 8], [18, 23]]]], [[('001', 7, 3, 2, 10), [[28, 29]]], [('1100000101000', 1, 1, 1, 1), [[1, 2], [8, 9], [10, 11]]], [('11000100111001', 5, 2, 1, 10), [[25, 29], [38, 39], [45, 52], [58, 59]]], [('1101101001', 3, 1, 0, 3), [[9, 15], [18, 24], [27, 30], [36, 39]]], [('100110010100', 1, 1, 0, 1), [[1, 2], [4, 6], [8, 9], [10, 11]]], [('101100', 4, 3, 1, 10), [[13, 14], [16, 18]]], [('0110001110', 2, 1, 0, 10), [[22, 26], [32, 38]]], [('00010110011', 7, 3, 2, 3), [[14, 15], [19, 21], [28, 31]]]], [[('101110001000', 9, 4, 2, 0), [[0, 1], [5, 9], [18, 19]]], [('110101100', 5, 2, 2, 0), [[0, 3], [8, 9], [13, 16]]], [('01100', 2, 1, 0, 0), [[2, 6]]], [('10110', 5, 2, 0, 0), [[0, 3], [5, 10]]], [('01110000', 2, 1, 0, 3), [[8, 14]]], [('00101011101', 7, 3, 1, 10), [[28, 29], [33, 34], [37, 43], [47, 48]]], [('10111010100111', 5, 2, 0, 1), [[3, 5], [8, 15], [18, 20], [23, 25], [30, 38]]], [('0000101000', 7, 3, 2, 3), [[16, 17], [21, 22]]]], [[('11111000001', 1, 1, 1, 0), [[0, 4], [10, 11]]], [('100', 1, 1, 2, 0), [[0, 1]]], [('011110111', 9, 4, 1, 10), [[25, 33], [36, 42]]], [('111', 4, 3, 2, 10), [[13, 15]]], [('10111101000110', 7, 3, 0, 3), [[7, 9], [12, 21], [23, 26], [33, 37]]], [('0111110010101', 7, 3, 0, 10), [[26, 37], [42, 44], [47, 49], [51, 54]]], [('1', 5, 2, 0, 3), [[8, 10]]], [('001000011', 1, 1, 1, 1), [[3, 4], [8, 9]]]]]
labels = ["regression: minimum bar width", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: minimum bar width 0[[2, 2], [7, 16]][[2, 3], [7, 16]]Failed
repair trap 1[[10, 11], [14, 16], [19, 19]][[10, 11], [14, 16], [19, 20]]Failed
combined fault 2[[8, 16]][[8, 16]]Passed
control 3[[28, 32]][[28, 32]]Passed
control 4[[5, 6], [7, 8]][[5, 6], [7, 8]]Passed
boundary 5[[0, 2], [4, 9], [13, 15], [18, 20]][[0, 2], [4, 9], [13, 15], [18, 20]]Passed
boundary 6[[6, 9], [12, 15]][[6, 9], [12, 15]]Passed
control 7[[1, 2], [8, 8]][[1, 2], [8, 9]]Failed

SHA-256 / 8fa35c1f842e5382a903c4bef2728b49bf00fb2586e16f9172ea84a2cc7cb7e5

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(mods, xn, xd, bwr, quiet):
    X = Fraction(xn, xd)
    def edge(i):
        return math.floor((quiet + i) * X + Fraction(1, 2))
    bars = []
    i = 0
    n = len(mods)
    while i < n:
        if mods[i] == '1':
            j = i
            while j < n and mods[j] == '1':
                j += 1
            s, e = edge(i), edge(j) - bwr
            if e < s:
                e = s
            bars.append([s, e])
            i = j
        else:
            i += 1
    return bars
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[('010111110', 11, 5, 2, 0), [[2, 3], [7, 16]]], [('1100111001', 1, 1, 1, 10), [[10, 11], [14, 16], [19, 20]]], [('0001111', 2, 1, 0, 1), [[8, 16]]], [('011', 5, 2, 1, 10), [[28, 32]]], [('00001010', 1, 1, 0, 1), [[5, 6], [7, 8]]], [('101100101', 11, 5, 0, 0), [[0, 2], [4, 9], [13, 15], [18, 20]]], [('00101', 3, 1, 0, 0), [[6, 9], [12, 15]]], [('11000100', 4, 3, 2, 1), [[1, 2], [8, 9]]]], [[('1', 4, 3, 1, 0), [[0, 1]]], [('00010000011', 11, 5, 2, 10), [[29, 30], [42, 44]]], [('0010101000110', 7, 3, 0, 0), [[5, 7], [9, 12], [14, 16], [23, 28]]], [('1111', 9, 4, 2, 3), [[7, 14]]], [('1100001111', 9, 4, 0, 0), [[0, 5], [14, 23]]], [('000010010001', 9, 4, 1, 0), [[9, 10], [16, 17], [25, 26]]], [('0011000', 3, 1, 2, 3), [[15, 19]]], [('10000111', 9, 4, 2, 3), [[7, 8], [18, 23]]]], [[('001', 7, 3, 2, 10), [[28, 29]]], [('1100000101000', 1, 1, 1, 1), [[1, 2], [8, 9], [10, 11]]], [('11000100111001', 5, 2, 1, 10), [[25, 29], [38, 39], [45, 52], [58, 59]]], [('1101101001', 3, 1, 0, 3), [[9, 15], [18, 24], [27, 30], [36, 39]]], [('100110010100', 1, 1, 0, 1), [[1, 2], [4, 6], [8, 9], [10, 11]]], [('101100', 4, 3, 1, 10), [[13, 14], [16, 18]]], [('0110001110', 2, 1, 0, 10), [[22, 26], [32, 38]]], [('00010110011', 7, 3, 2, 3), [[14, 15], [19, 21], [28, 31]]]], [[('101110001000', 9, 4, 2, 0), [[0, 1], [5, 9], [18, 19]]], [('110101100', 5, 2, 2, 0), [[0, 3], [8, 9], [13, 16]]], [('01100', 2, 1, 0, 0), [[2, 6]]], [('10110', 5, 2, 0, 0), [[0, 3], [5, 10]]], [('01110000', 2, 1, 0, 3), [[8, 14]]], [('00101011101', 7, 3, 1, 10), [[28, 29], [33, 34], [37, 43], [47, 48]]], [('10111010100111', 5, 2, 0, 1), [[3, 5], [8, 15], [18, 20], [23, 25], [30, 38]]], [('0000101000', 7, 3, 2, 3), [[16, 17], [21, 22]]]], [[('11111000001', 1, 1, 1, 0), [[0, 4], [10, 11]]], [('100', 1, 1, 2, 0), [[0, 1]]], [('011110111', 9, 4, 1, 10), [[25, 33], [36, 42]]], [('111', 4, 3, 2, 10), [[13, 15]]], [('10111101000110', 7, 3, 0, 3), [[7, 9], [12, 21], [23, 26], [33, 37]]], [('0111110010101', 7, 3, 0, 10), [[26, 37], [42, 44], [47, 49], [51, 54]]], [('1', 5, 2, 0, 3), [[8, 10]]], [('001000011', 1, 1, 1, 1), [[3, 4], [8, 9]]]]]
labels = ["regression: minimum bar width", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: minimum bar width 0[[2, 2], [7, 16]][[2, 3], [7, 16]]Failed
repair trap 1[[10, 11], [14, 16], [19, 19]][[10, 11], [14, 16], [19, 20]]Failed
combined fault 2[[8, 16]][[8, 16]]Passed
control 3[[28, 32]][[28, 32]]Passed
control 4[[5, 6], [7, 8]][[5, 6], [7, 8]]Passed
boundary 5[[0, 2], [4, 9], [13, 15], [18, 20]][[0, 2], [4, 9], [13, 15], [18, 20]]Passed
boundary 6[[6, 9], [12, 15]][[6, 9], [12, 15]]Passed
control 7[[1, 2], [8, 8]][[1, 2], [8, 9]]Failed

SHA-256 / 8a03bd6a0d79544ad90c299ddf95bf791a15f8821805d611611e1b8d968ad0e8

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic bounded teaching model with a stipulated contract; it makes no claim of conformance to any published specification. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:49:47.576833+00:00.

Case digest / d507775e62c2e8bb9128469aa40e0da2d3dc67ef32422ca0f976530e05504f77