FA-78955 / Image orientation metadata / Member archive

Vertical flip is applied in stored rather than displayed orientation · case 05

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

Member previewVariant 5 · 3 implementations · 8 checks per implementation

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.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: vertical flip of a rotated view 0	`6`	`8`	Failed

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