FA-79310 / Image orientation metadata / Member archive

Canonical key flattens the grid column by column · case 05

Two services computing the canonical form disagree because one flattens column-major.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

For duplicate detection, bring a pixel grid into a canonical orientation: of the eight orientations (tags 1..8, same pixel mapping as EXIF baking), pick the one whose key (height, width, row-major pixels) is smallest; ties go to the lowest tag. Return [tag, inverse_tag, canonical_grid] where the inverse tag restores the original (6 and 8 are mutual inverses, every other tag is self-inverse).

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.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: pixel order in the key 0	`[4, 4, [[1, 8, 5], [2, 8, 2], [3, 4, 2]]]`	`[6, 8, [[1, 2, 3], [8, 8, 4], [5, 2, 2]]]`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.