{"abstract":"A straight source channel is treated as already premultiplied.","category":"Raster compositing","checks":4,"contract":"Return a normalized straight source channel composited over an opaque destination channel. All three inputs lie in [0,1].","evaluation_group":"xg-straight-alpha-source-over-channel","failed_approach":"Attenuating the source without attenuating the destination double-counts covered background.","family":"xg-straight-alpha-source-over-channel","id":"FA-10531","implementations":{"attempt":{"sha256":"20ddbe3cf3262a0d018d670d6b08eef08b60dd8476c78bdf89d7f0fe97828f03","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(source, alpha, destination):\n    return source*alpha+destination\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(0.8, 0.5, 0.2)), 0.5)\ncheck('fixture 2', solve(*(1, 0, 0.25)), 0.25)\ncheck('fixture 3', solve(*(0.25, 1, 0.8)), 0.25)\ncheck('fixture 4', solve(*(0, 0.5, 1)), 0.5)\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":"0973a9f51c4d44832e114951374ec010f4725a512eaf130dc9f9639b1b4f645e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(source, alpha, destination):\n    return source+destination*(1-alpha)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(0.8, 0.5, 0.2)), 0.5)\ncheck('fixture 2', solve(*(1, 0, 0.25)), 0.25)\ncheck('fixture 3', solve(*(0.25, 1, 0.8)), 0.25)\ncheck('fixture 4', solve(*(0, 0.5, 1)), 0.5)\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":"d64e0fc59f1c154fdfbb72cc53cefb716307862f26742a3920eb6122094c26a2","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(source, alpha, destination):\n    return source*alpha+destination*(1-alpha)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(0.8, 0.5, 0.2)), 0.5)\ncheck('fixture 2', solve(*(1, 0, 0.25)), 0.25)\ncheck('fixture 3', solve(*(0.25, 1, 0.8)), 0.25)\ncheck('fixture 4', solve(*(0, 0.5, 1)), 0.5)\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-straight-alpha-source-over-channel","generated_at":"2026-09-29T14:38:39.898946+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: Return a normalized straight source channel composited over an opaque destination channel. All three inputs lie in [0,1].","root_cause":"A straight source channel is treated as already premultiplied.","sha256":"67d7ae6732fc1c5efc8a6bbaa9b98feac51d36a97c12522c24e69adc8283dfb9","title":"Straight alpha source over channel · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":39.09,"exit_code":1,"observations":[{"actual":0.6000000000000001,"check":"fixture 1","expected":0.5,"passed":false},{"actual":0.25,"check":"fixture 2","expected":0.25,"passed":true},{"actual":1.05,"check":"fixture 3","expected":0.25,"passed":false},{"actual":1.0,"check":"fixture 4","expected":0.5,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": 0.6000000000000001, \"expected\": 0.5, \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": 0.25, \"expected\": 0.25, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 1.05, \"expected\": 0.25, \"passed\": false}, {\"check\": \"fixture 4\", \"actual\": 1.0, \"expected\": 0.5, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":38.972,"exit_code":1,"observations":[{"actual":0.9,"check":"fixture 1","expected":0.5,"passed":false},{"actual":1.25,"check":"fixture 2","expected":0.25,"passed":false},{"actual":0.25,"check":"fixture 3","expected":0.25,"passed":true},{"actual":0.5,"check":"fixture 4","expected":0.5,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": 0.9, \"expected\": 0.5, \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": 1.25, \"expected\": 0.25, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": 0.25, \"expected\": 0.25, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 0.5, \"expected\": 0.5, \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":45.277,"exit_code":0,"observations":[{"actual":0.5,"check":"fixture 1","expected":0.5,"passed":true},{"actual":0.25,"check":"fixture 2","expected":0.25,"passed":true},{"actual":0.25,"check":"fixture 3","expected":0.25,"passed":true},{"actual":0.5,"check":"fixture 4","expected":0.5,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": 0.5, \"expected\": 0.5, \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": 0.25, \"expected\": 0.25, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 0.25, \"expected\": 0.25, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 0.5, \"expected\": 0.5, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}