FA-10581 / Raster compositing / Open access
Screen blend complement product · case 01
Multiplication computes a darkening blend rather than screen.
ROOT CAUSE
Multiplication computes a darkening blend rather than screen.
THE FAILURE
Multiplication computes a darkening blend rather than screen.
Unsuccessful approach: Saturated addition ignores the overlap correction.
Case contract
Return screen blending for two normalized straight color channels.
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(source, destination):
return source*destination
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(0.5, 0.5)), 0.75)
check('fixture 2', solve(*(0, 0.25)), 0.25)
check('fixture 3', solve(*(1, 0.25)), 1)
check('fixture 4', solve(*(0.25, 0.5)), 0.625)
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 | 0.25 | 0.75 | Failed |
| fixture 2 | 0.0 | 0.25 | Failed |
| fixture 3 | 0.25 | 1 | Failed |
| fixture 4 | 0.125 | 0.625 | Failed |
SHA-256 / b7ef96f7b774c0d6ebf13584661b095d9e98cbf4540e6411c1e1a4e48d900d4b
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(source, destination):
return min(1,source+destination)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(0.5, 0.5)), 0.75)
check('fixture 2', solve(*(0, 0.25)), 0.25)
check('fixture 3', solve(*(1, 0.25)), 1)
check('fixture 4', solve(*(0.25, 0.5)), 0.625)
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 | 0.75 | Failed |
| fixture 2 | 0.25 | 0.25 | Passed |
| fixture 3 | 1 | 1 | Passed |
| fixture 4 | 0.75 | 0.625 | Failed |
SHA-256 / 15fcdbd9103b5c9c013d4201c7912622521ee60d9444e82cf939e356f1884de7
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 4 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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Sign in to the archive ↗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 2026-09-29T14:38:40.346205+00:00.
Case digest / e1c10df78f296665f8bbdc57268944de93e001fa221577068a50c03853a42f9e