FA-79285 / Image orientation metadata / Member archive

Tap position is rounded to the nearest pixel corner · case 05

Taps in the right half of a pixel select its neighbour.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

A viewer letterboxes the displayed image (contain fit, centred) inside a view [vw, vh]. Map a tap [tx, ty] in view coordinates to the stored pixel [x, y] of an image of stored size [w, h] with orientation tag 1..8 (invalid -> 1); tags 5..8 swap displayed axes. Taps in the letterbox bars or on the far edge return None; the displayed pixel is floor of the exact position, then mapped back through the inverse of the orientation.

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: displayed pixel quantisation 0	`[1, 6]`	`[2, 5]`	Failed

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