FA-10611 / Color encoding / Open access
Byte channel normalization · case 01
Dividing by 256 makes the maximum representable white less than one.
ROOT CAUSE
Dividing by 256 makes the maximum representable white less than one.
VERIFIED REPAIR
Use the stage contract: Map integer byte values in [0,255] to normalized [0,1] with both endpoints exact.
Unsuccessful approach: Integer division reduces nearly all nonwhite channels to black.
Case contract
Map integer byte values in [0,255] to normalized [0,1] with both endpoints exact.
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(byte):
return byte/256
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(255,)), 1)
check('fixture 2', solve(*(0,)), 0)
check('fixture 3', solve(*(85,)), 0.3333333333333333)
check('fixture 4', solve(*(128,)), 0.5019607843137255)
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 | 0.99609375 | 1 | Failed |
| fixture 2 | 0.0 | 0 | Passed |
| fixture 3 | 0.33203125 | 0.3333333333333333 | Failed |
| fixture 4 | 0.5 | 0.5019607843137255 | Failed |
SHA-256 / b17b00cebb088a4e4138bfeab1b27bfb43c52eff055c2951b82a268740a5d38d
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(byte):
return byte//255
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(255,)), 1)
check('fixture 2', solve(*(0,)), 0)
check('fixture 3', solve(*(85,)), 0.3333333333333333)
check('fixture 4', solve(*(128,)), 0.5019607843137255)
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 | 1 | Passed |
| fixture 2 | 0 | 0 | Passed |
| fixture 3 | 0 | 0.3333333333333333 | Failed |
| fixture 4 | 0 | 0.5019607843137255 | Failed |
SHA-256 / 591e377c0a1dafec26e763aa211ad69f535db974c7f7a0edb4b4d437f8aed3d4
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(byte):
return byte/255
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(255,)), 1)
check('fixture 2', solve(*(0,)), 0)
check('fixture 3', solve(*(85,)), 0.3333333333333333)
check('fixture 4', solve(*(128,)), 0.5019607843137255)
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 | 1.0 | 1 | Passed |
| fixture 2 | 0.0 | 0 | Passed |
| fixture 3 | 0.3333333333333333 | 0.3333333333333333 | Passed |
| fixture 4 | 0.5019607843137255 | 0.5019607843137255 | Passed |
SHA-256 / a73f82f808cb53fc2d201e393ff48d66bd5c516db98b8086f54615aba81c405a
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 2026-09-29T14:38:40.582287+00:00.
Case digest / f8ef3bed0e2f789b4a44a468816b7f75d1158cba233607a7b3b7204b0dcd930b