FA-79183 / Image orientation metadata / Member archive

Canvas mirror uses the pixel-index offset · case 03

Mirrored images are drawn one pixel to the left with a transparent column on the right.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input [w, h, tag]. Produce the canvas size and the 2D affine [a, b, c, d, e, f] (x' = a*x + c*y + e, y' = b*x + d*y + f, continuous coordinates, so mirroring an extent e maps x to e - x) that draws the stored image upright. Tags 5..8 use a [h, w] canvas; invalid tags are treated as 1.

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: horizontal mirror offset 0	`{"canvas": [2623, 3832], "matrix": [-1, 0, 0, 1, 2622, 0]}`	`{"canvas": [2623, 3832], "matrix": [-1, 0, 0, 1, 2623, 0]}`	Failed

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