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FA-78951 / Image orientation metadata / Open access

Vertical flip is applied in stored rather than displayed orientation · case 01

Flip top-bottom on a rotated image flips it left-right on screen.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

flip_v adds a half turn without reversing the existing rotation.

VERIFIED REPAIR

A top-bottom mirror equals a half turn after a left-right mirror, so the new count is (2 - k) mod 4.

Unsuccessful approach: Reusing the flip_h rule drops the extra half turn entirely.

Case contract

A photo editor rotates and flips losslessly by rewriting only the orientation tag. An orientation is modelled as (k, m): mirror horizontally m times, then rotate k quarter turns clockwise (tag table 1:(0,0) 2:(0,1) 3:(2,0) 4:(2,1) 5:(3,1) 6:(1,0) 7:(1,1) 8:(3,0)). Editor operations act on the displayed image: cw, ccw, r180, flip_h (mirror left-right) and flip_v (mirror top-bottom). Invalid starting tags count as 1; an unknown operation returns {"error": "unknown-op", "op": op}. Return the final tag.

Why this case matters

Camera, phone and scanner images carry an orientation hint separately from the stored pixels; galleries, thumbnailers, editors and upload pipelines must interpret it consistently or photos appear sideways, mirrored or doubly rotated.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(tag, ops):
    to_km = {1: (0, 0), 2: (0, 1), 3: (2, 0), 4: (2, 1), 5: (3, 1), 6: (1, 0), 7: (1, 1), 8: (3, 0)}
    from_km = {v: t for t, v in to_km.items()}
    if tag not in to_km:
        tag = 1
    k, m = to_km[tag]
    for op in ops:
        if op == 'cw':
            k = (k + 1) % 4
        elif op == 'ccw':
            k = (k + 3) % 4
        elif op == 'r180':
            k = (k + 2) % 4
        elif op == 'flip_h':
            k, m = (-k) % 4, 1 - m
        elif op == 'flip_v':
            k, m = (k + 2) % 4, 1 - m
        else:
            return {'error': 'unknown-op', 'op': op}
    return from_km[(k, m)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[(7, ['flip_v', 'ccw', 'r180']), 3], [(0, ['ccw', 'flip_v', 'r180', 'cw']), 4], [(8, ['ccw', 'flip_h', 'ccw']), 7], [(8, ['ccw', 'cw']), 8], [(3, ['rotate']), {'error': 'unknown-op', 'op': 'rotate'}], [(1, ['cw', 'ccw', 'r180', 'cw']), 8], [(6, []), 6], [(3, ['flip_h', 'cw', 'flip_v', 'flip_h']), 7]], [[(11, ['ccw', 'flip_v', 'ccw', 'ccw']), 7], [(7, ['r180', 'ccw', 'flip_v', 'cw']), 6], [(7, ['flip_h', 'flip_v']), 5], [(8, ['CW']), {'error': 'unknown-op', 'op': 'CW'}], [(0, []), 1], [(8, ['ccw', 'r180']), 1], [(4, ['mirror', 'flip_v', 'cw', 'r180']), {'error': 'unknown-op', 'op': 'mirror'}], [(3, ['ccw', 'flip_v', 'flip_h', 'flip_h']), 7]], [[(6, ['r180', 'flip_v', 'ccw']), 4], [(11, ['cw', 'flip_v', 'flip_h']), 8], [(2, ['ccw', 'cw', 'cw', 'flip_v']), 6], [(1, ['ccw', 'ccw', 'r180']), 1], [(9, ['cw', 'r180', 'flip_h']), 7], [(5, ['flip_h']), 6], [(6, ['flip_h', 'flip_h', 'ccw', 'r180']), 3], [(2, ['r180', 'ccw', 'flip_h', 'flip_v']), 5]], [[(5, ['flip_h', 'flip_v', 'r180']), 5], [(9, ['ccw', 'flip_h', 'flip_v']), 6], [(0, ['ccw', 'flip_v']), 5], [(4, ['ccw']), 7], [(8, ['rotate']), {'error': 'unknown-op', 'op': 'rotate'}], [(11, ['r180']), 3], [(8, ['ccw', 'r180', 'ccw']), 8], [(1, ['r180', 'flip_h', 'cw', 'flip_v']), 8]], [[(7, ['r180', 'flip_v']), 8], [(0, ['flip_v', 'cw']), 5], [(8, ['flip_v', 'ccw', 'flip_h', 'ccw']), 6], [(11, ['cw', 'cw', 'ccw']), 6], [(5, ['r180']), 7], [(6, ['ccw']), 1], [(0, ['ccw', 'cw']), 1], [(6, ['flip_h', 'flip_v', 'flip_h']), 7]]]
labels = ["regression: vertical flip of a rotated view", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(*args), expected)
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 fixtureActualExpectedOutcome
regression: vertical flip of a rotated view 013Failed
repair trap 124Failed
combined fault 277Passed
control 388Passed
control 4{'error': 'unknown-op', 'op': 'rotate'}{'error': 'unknown-op', 'op': 'rotate'}Passed
boundary 588Passed
boundary 666Passed
control 757Failed

SHA-256 / 772b61b341fc3693999b6dbaf817e5d9676b577d890405ebca2e1b2ecb472b6f

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(tag, ops):
    to_km = {1: (0, 0), 2: (0, 1), 3: (2, 0), 4: (2, 1), 5: (3, 1), 6: (1, 0), 7: (1, 1), 8: (3, 0)}
    from_km = {v: t for t, v in to_km.items()}
    if tag not in to_km:
        tag = 1
    k, m = to_km[tag]
    for op in ops:
        if op == 'cw':
            k = (k + 1) % 4
        elif op == 'ccw':
            k = (k + 3) % 4
        elif op == 'r180':
            k = (k + 2) % 4
        elif op == 'flip_h':
            k, m = (-k) % 4, 1 - m
        elif op == 'flip_v':
            k, m = (-k) % 4, 1 - m
        else:
            return {'error': 'unknown-op', 'op': op}
    return from_km[(k, m)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[(7, ['flip_v', 'ccw', 'r180']), 3], [(0, ['ccw', 'flip_v', 'r180', 'cw']), 4], [(8, ['ccw', 'flip_h', 'ccw']), 7], [(8, ['ccw', 'cw']), 8], [(3, ['rotate']), {'error': 'unknown-op', 'op': 'rotate'}], [(1, ['cw', 'ccw', 'r180', 'cw']), 8], [(6, []), 6], [(3, ['flip_h', 'cw', 'flip_v', 'flip_h']), 7]], [[(11, ['ccw', 'flip_v', 'ccw', 'ccw']), 7], [(7, ['r180', 'ccw', 'flip_v', 'cw']), 6], [(7, ['flip_h', 'flip_v']), 5], [(8, ['CW']), {'error': 'unknown-op', 'op': 'CW'}], [(0, []), 1], [(8, ['ccw', 'r180']), 1], [(4, ['mirror', 'flip_v', 'cw', 'r180']), {'error': 'unknown-op', 'op': 'mirror'}], [(3, ['ccw', 'flip_v', 'flip_h', 'flip_h']), 7]], [[(6, ['r180', 'flip_v', 'ccw']), 4], [(11, ['cw', 'flip_v', 'flip_h']), 8], [(2, ['ccw', 'cw', 'cw', 'flip_v']), 6], [(1, ['ccw', 'ccw', 'r180']), 1], [(9, ['cw', 'r180', 'flip_h']), 7], [(5, ['flip_h']), 6], [(6, ['flip_h', 'flip_h', 'ccw', 'r180']), 3], [(2, ['r180', 'ccw', 'flip_h', 'flip_v']), 5]], [[(5, ['flip_h', 'flip_v', 'r180']), 5], [(9, ['ccw', 'flip_h', 'flip_v']), 6], [(0, ['ccw', 'flip_v']), 5], [(4, ['ccw']), 7], [(8, ['rotate']), {'error': 'unknown-op', 'op': 'rotate'}], [(11, ['r180']), 3], [(8, ['ccw', 'r180', 'ccw']), 8], [(1, ['r180', 'flip_h', 'cw', 'flip_v']), 8]], [[(7, ['r180', 'flip_v']), 8], [(0, ['flip_v', 'cw']), 5], [(8, ['flip_v', 'ccw', 'flip_h', 'ccw']), 6], [(11, ['cw', 'cw', 'ccw']), 6], [(5, ['r180']), 7], [(6, ['ccw']), 1], [(0, ['ccw', 'cw']), 1], [(6, ['flip_h', 'flip_v', 'flip_h']), 7]]]
labels = ["regression: vertical flip of a rotated view", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(*args), expected)
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 fixtureActualExpectedOutcome
regression: vertical flip of a rotated view 013Failed
repair trap 124Failed
combined fault 277Passed
control 388Passed
control 4{'error': 'unknown-op', 'op': 'rotate'}{'error': 'unknown-op', 'op': 'rotate'}Passed
boundary 588Passed
boundary 666Passed
control 757Failed

SHA-256 / 19abedddac71502c122f6b3848c1308577bd7a1319edd8bc24c6cea932da6cca

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(tag, ops):
    to_km = {1: (0, 0), 2: (0, 1), 3: (2, 0), 4: (2, 1), 5: (3, 1), 6: (1, 0), 7: (1, 1), 8: (3, 0)}
    from_km = {v: t for t, v in to_km.items()}
    if tag not in to_km:
        tag = 1
    k, m = to_km[tag]
    for op in ops:
        if op == 'cw':
            k = (k + 1) % 4
        elif op == 'ccw':
            k = (k + 3) % 4
        elif op == 'r180':
            k = (k + 2) % 4
        elif op == 'flip_h':
            k, m = (-k) % 4, 1 - m
        elif op == 'flip_v':
            k, m = (2 - k) % 4, 1 - m
        else:
            return {'error': 'unknown-op', 'op': op}
    return from_km[(k, m)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[(7, ['flip_v', 'ccw', 'r180']), 3], [(0, ['ccw', 'flip_v', 'r180', 'cw']), 4], [(8, ['ccw', 'flip_h', 'ccw']), 7], [(8, ['ccw', 'cw']), 8], [(3, ['rotate']), {'error': 'unknown-op', 'op': 'rotate'}], [(1, ['cw', 'ccw', 'r180', 'cw']), 8], [(6, []), 6], [(3, ['flip_h', 'cw', 'flip_v', 'flip_h']), 7]], [[(11, ['ccw', 'flip_v', 'ccw', 'ccw']), 7], [(7, ['r180', 'ccw', 'flip_v', 'cw']), 6], [(7, ['flip_h', 'flip_v']), 5], [(8, ['CW']), {'error': 'unknown-op', 'op': 'CW'}], [(0, []), 1], [(8, ['ccw', 'r180']), 1], [(4, ['mirror', 'flip_v', 'cw', 'r180']), {'error': 'unknown-op', 'op': 'mirror'}], [(3, ['ccw', 'flip_v', 'flip_h', 'flip_h']), 7]], [[(6, ['r180', 'flip_v', 'ccw']), 4], [(11, ['cw', 'flip_v', 'flip_h']), 8], [(2, ['ccw', 'cw', 'cw', 'flip_v']), 6], [(1, ['ccw', 'ccw', 'r180']), 1], [(9, ['cw', 'r180', 'flip_h']), 7], [(5, ['flip_h']), 6], [(6, ['flip_h', 'flip_h', 'ccw', 'r180']), 3], [(2, ['r180', 'ccw', 'flip_h', 'flip_v']), 5]], [[(5, ['flip_h', 'flip_v', 'r180']), 5], [(9, ['ccw', 'flip_h', 'flip_v']), 6], [(0, ['ccw', 'flip_v']), 5], [(4, ['ccw']), 7], [(8, ['rotate']), {'error': 'unknown-op', 'op': 'rotate'}], [(11, ['r180']), 3], [(8, ['ccw', 'r180', 'ccw']), 8], [(1, ['r180', 'flip_h', 'cw', 'flip_v']), 8]], [[(7, ['r180', 'flip_v']), 8], [(0, ['flip_v', 'cw']), 5], [(8, ['flip_v', 'ccw', 'flip_h', 'ccw']), 6], [(11, ['cw', 'cw', 'ccw']), 6], [(5, ['r180']), 7], [(6, ['ccw']), 1], [(0, ['ccw', 'cw']), 1], [(6, ['flip_h', 'flip_v', 'flip_h']), 7]]]
labels = ["regression: vertical flip of a rotated view", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(*args), expected)
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 fixtureActualExpectedOutcome
regression: vertical flip of a rotated view 033Passed
repair trap 144Passed
combined fault 277Passed
control 388Passed
control 4{'error': 'unknown-op', 'op': 'rotate'}{'error': 'unknown-op', 'op': 'rotate'}Passed
boundary 588Passed
boundary 666Passed
control 777Passed

SHA-256 / 5f9fff84fed45582a0b28dfb9a217d717cdea16028c833ed7a73aba377540e0c

Verification & scope

A deterministic bounded teaching model with a stipulated contract; it makes no claim of conformance to any published specification. 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 2026-09-29T14:49:39.925045+00:00.

Case digest / 08fdd4938fb4e0fa65ad0bef2993278cf33d6e04010cbe2746be53dab1fb9cf3