FA-79118 / Image orientation metadata / Member archive

Baking a rotated scan leaves X and Y resolution unswapped · case 03

Anisotropic scans print stretched after their pixels were rotated upright.

Member previewVariant 3 · 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: resolution pair swap 0	`[["ImageLength", 1422], ["ImageWidth", 2871], ["Orientation", 1], ["PixelXDimension", 2248], ["PixelYDimension", 1678], ["XMP:Orientation", "1"], ["YResolution", 243]]`	`[["ImageLength", 1422], ["ImageWidth", 2871], ["Orientation", 1], ["PixelXDimension", 2248], ["PixelYDimension", 1678], ["XMP:Orientation", "1"], ["XResolution", 243]]`	Failed

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