FA-79140 / Image orientation metadata / Member archive

Regenerated thumbnail keeps a thumbnail orientation tag · case 05

Viewers that trust the thumbnail tag show a stale value for the regenerated thumbnail.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

After pixels have been baked upright, rewrite the metadata dictionary. When the (valid) Orientation is 5..8, exchange PixelXDimension/PixelYDimension, ImageWidth/ImageLength and XResolution/YResolution, moving a lone member of a pair to its partner key. Invalid or missing Orientation values mean no swap. Orientation is set to 1 only if the key exists; XMP:Orientation, if present, becomes the string "1"; ThumbOrientation is removed because the thumbnail is regenerated. Return sorted [key, value] pairs.

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: thumbnail orientation removal 0	`[["ImageLength", 4709], ["ImageWidth", 3039], ["Make", "Acme"], ["Orientation", 1], ["PixelYDimension", 1209], ["ThumbOrientation", 1], ["XMP:Orientation", "1"], ["XResolution", 133], ["YResolution", 298]]`	`[["ImageLength", 4709], ["ImageWidth", 3039], ["Make", "Acme"], ["Orientation", 1], ["PixelYDimension", 1209], ["XMP:Orientation", "1"], ["XResolution", 133], ["YResolution", 298]]`	Failed

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

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