{"abstract":"Premultiplied channels are exposed as straight channels and darken translucent pixels.","category":"Raster compositing","checks":4,"contract":"Input is valid premultiplied normalized RGBA. Divide RGB by nonzero alpha; represent fully transparent output as transparent black.","evaluation_group":"xg-unpremultiply-transparent-color","failed_approach":"Clamping the divisor to at least one prevents recovery of every translucent color.","family":"xg-unpremultiply-transparent-color","id":"FA-10551","implementations":{"attempt":{"sha256":"a81736c896c2763ce8b16b4ddf5a999bef199bceb1efcc9c21aac45ae437e6a0","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(rgba):\n    return [x/max(rgba[3],1) for x in rgba[:3]]+[rgba[3]]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*([0.5, 0.25, 0.125, 0.5],)), [1, 0.5, 0.25, 0.5])\ncheck('fixture 2', solve(*([0, 0, 0, 0],)), [0, 0, 0, 0])\ncheck('fixture 3', solve(*([0.25, 0.5, 1, 1],)), [0.25, 0.5, 1, 1])\ncheck('fixture 4', solve(*([0, 0.125, 0, 0.25],)), [0, 0.5, 0, 0.25])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"c8cc2b137706f9ba920ae8bbac41bac2edc3aa0a0eb69149fa89d457144a2c07","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(rgba):\n    return list(rgba)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*([0.5, 0.25, 0.125, 0.5],)), [1, 0.5, 0.25, 0.5])\ncheck('fixture 2', solve(*([0, 0, 0, 0],)), [0, 0, 0, 0])\ncheck('fixture 3', solve(*([0.25, 0.5, 1, 1],)), [0.25, 0.5, 1, 1])\ncheck('fixture 4', solve(*([0, 0.125, 0, 0.25],)), [0, 0.5, 0, 0.25])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"9dc451a49115751130e4e202a1b3cd340f49d1bfa33be38650252427db1f37e7","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(rgba):\n    return [x/rgba[3] for x in rgba[:3]]+[rgba[3]] if rgba[3] else [0,0,0,0]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*([0.5, 0.25, 0.125, 0.5],)), [1, 0.5, 0.25, 0.5])\ncheck('fixture 2', solve(*([0, 0, 0, 0],)), [0, 0, 0, 0])\ncheck('fixture 3', solve(*([0.25, 0.5, 1, 1],)), [0.25, 0.5, 1, 1])\ncheck('fixture 4', solve(*([0, 0.125, 0, 0.25],)), [0, 0.5, 0, 0.25])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":" 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.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xg-unpremultiply-transparent-color","generated_at":"2026-09-29T14:38:39.947725+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic software graphics stage with explicit channel and coordinate conventions; no hardware, device profile or API behavior is inferred.","repair":"Use the stage contract: Input is valid premultiplied normalized RGBA. Divide RGB by nonzero alpha; represent fully transparent output as transparent black.","root_cause":"Premultiplied channels are exposed as straight channels and darken translucent pixels.","sha256":"ef173c845c78137cbd55764e61e6cc5738cec818e18e5e53246f3672992912cd","title":"Unpremultiply transparent color · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":43.027,"exit_code":1,"observations":[{"actual":[0.5,0.25,0.125,0.5],"check":"fixture 1","expected":[1,0.5,0.25,0.5],"passed":false},{"actual":[0.0,0.0,0.0,0],"check":"fixture 2","expected":[0,0,0,0],"passed":true},{"actual":[0.25,0.5,1.0,1],"check":"fixture 3","expected":[0.25,0.5,1,1],"passed":true},{"actual":[0.0,0.125,0.0,0.25],"check":"fixture 4","expected":[0,0.5,0,0.25],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [0.5, 0.25, 0.125, 0.5], \"expected\": [1, 0.5, 0.25, 0.5], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [0.0, 0.0, 0.0, 0], \"expected\": [0, 0, 0, 0], \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": [0.25, 0.5, 1.0, 1], \"expected\": [0.25, 0.5, 1, 1], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [0.0, 0.125, 0.0, 0.25], \"expected\": [0, 0.5, 0, 0.25], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.069,"exit_code":1,"observations":[{"actual":[0.5,0.25,0.125,0.5],"check":"fixture 1","expected":[1,0.5,0.25,0.5],"passed":false},{"actual":[0,0,0,0],"check":"fixture 2","expected":[0,0,0,0],"passed":true},{"actual":[0.25,0.5,1,1],"check":"fixture 3","expected":[0.25,0.5,1,1],"passed":true},{"actual":[0,0.125,0,0.25],"check":"fixture 4","expected":[0,0.5,0,0.25],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [0.5, 0.25, 0.125, 0.5], \"expected\": [1, 0.5, 0.25, 0.5], \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": [0, 0, 0, 0], \"expected\": [0, 0, 0, 0], \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": [0.25, 0.5, 1, 1], \"expected\": [0.25, 0.5, 1, 1], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [0, 0.125, 0, 0.25], \"expected\": [0, 0.5, 0, 0.25], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":41.917,"exit_code":0,"observations":[{"actual":[1.0,0.5,0.25,0.5],"check":"fixture 1","expected":[1,0.5,0.25,0.5],"passed":true},{"actual":[0,0,0,0],"check":"fixture 2","expected":[0,0,0,0],"passed":true},{"actual":[0.25,0.5,1.0,1],"check":"fixture 3","expected":[0.25,0.5,1,1],"passed":true},{"actual":[0.0,0.5,0.0,0.25],"check":"fixture 4","expected":[0,0.5,0,0.25],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": [1.0, 0.5, 0.25, 0.5], \"expected\": [1, 0.5, 0.25, 0.5], \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": [0, 0, 0, 0], \"expected\": [0, 0, 0, 0], \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": [0.25, 0.5, 1.0, 1], \"expected\": [0.25, 0.5, 1, 1], \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": [0.0, 0.5, 0.0, 0.25], \"expected\": [0, 0.5, 0, 0.25], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}