FA-10601 / Color encoding / Open access

Unpack rgba byte mask · case 01

Shifted higher-order channels leak into lower byte values.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Shifted higher-order channels leak into lower byte values.

VERIFIED REPAIR

Use the stage contract: Unpack a 32-bit unsigned big-endian RGBA integer into four bytes, masking each shifted field.

Unsuccessful approach: Masking with reversed shifts yields ABGR instead of RGBA.

Case contract

Unpack a 32-bit unsigned big-endian RGBA integer into four bytes, masking each shifted field.

Why this case matters

A deterministic software graphics stage with explicit channel and coordinate conventions; no hardware, device profile or API behavior is inferred.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(word):
    return [word>>shift for shift in (24,16,8,0)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(16909060,)), [1, 2, 3, 4])
check('fixture 2', solve(*(255,)), [0, 0, 0, 255])
check('fixture 3', solve(*(4278190080,)), [255, 0, 0, 0])
check('fixture 4', solve(*(0,)), [0, 0, 0, 0])
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 fixture	Actual	Expected	Outcome
fixture 1	`[1, 258, 66051, 16909060]`	`[1, 2, 3, 4]`	Failed
fixture 2	`[0, 0, 0, 255]`	`[0, 0, 0, 255]`	Passed
fixture 3	`[255, 65280, 16711680, 4278190080]`	`[255, 0, 0, 0]`	Failed
fixture 4	`[0, 0, 0, 0]`	`[0, 0, 0, 0]`	Passed

SHA-256 / 9068dd00ecbc5115004c35edd2f31fe704746ac8ddbb7535ada3d25f07dc42c8

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(word):
    return [(word>>shift)&255 for shift in (0,8,16,24)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(16909060,)), [1, 2, 3, 4])
check('fixture 2', solve(*(255,)), [0, 0, 0, 255])
check('fixture 3', solve(*(4278190080,)), [255, 0, 0, 0])
check('fixture 4', solve(*(0,)), [0, 0, 0, 0])
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 fixture	Actual	Expected	Outcome
fixture 1	`[4, 3, 2, 1]`	`[1, 2, 3, 4]`	Failed
fixture 2	`[255, 0, 0, 0]`	`[0, 0, 0, 255]`	Failed
fixture 3	`[0, 0, 0, 255]`	`[255, 0, 0, 0]`	Failed
fixture 4	`[0, 0, 0, 0]`	`[0, 0, 0, 0]`	Passed

SHA-256 / 39e856bf5ae26023d14a57aacd32d827ba4200e78ef625391fcf81e28d3cda00

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(word):
    return [(word>>shift)&255 for shift in (24,16,8,0)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(16909060,)), [1, 2, 3, 4])
check('fixture 2', solve(*(255,)), [0, 0, 0, 255])
check('fixture 3', solve(*(4278190080,)), [255, 0, 0, 0])
check('fixture 4', solve(*(0,)), [0, 0, 0, 0])
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 fixture	Actual	Expected	Outcome
fixture 1	`[1, 2, 3, 4]`	`[1, 2, 3, 4]`	Passed
fixture 2	`[0, 0, 0, 255]`	`[0, 0, 0, 255]`	Passed
fixture 3	`[255, 0, 0, 0]`	`[255, 0, 0, 0]`	Passed
fixture 4	`[0, 0, 0, 0]`	`[0, 0, 0, 0]`	Passed

SHA-256 / ce0f087a200f7893efd8a85a9e9575b821c2e5afa44fbd6ea38cb73d6515eab8

Verification & scope

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 2026-09-29T14:38:40.540260+00:00.

Case digest / 899cb12dc24029adc799e9be97c09dfa93714d75a67045df00cb44d2405d662d