`_read_display_tags` drops the orientation when the raster no longer has the
source's stored dimensions, which is what stops an upright decode from being
tagged into a second rotation. It read those dimensions off `Image.size`.
That is not the stored size for TIFF: Pillow's TIFF reader applies the EXIF
orientation itself and reports the upright one. For a transposing orientation
the comparison was upright-against-upright, so it matched and the tag rode
along onto pixels that were already turned. `erase` on a 96x64 TIFF tagged 6
returned a 64x96 PNG carrying Orientation 6, and a viewer turned it again.
The TIFF IFD keeps the real geometry in ImageWidth/ImageLength, and no other
Pillow plugin exposes `tag_v2`, so every other container falls back to
`Image.size` and is byte-for-byte unaffected.
Also corrects `_pil_read`'s "No EXIF auto-rotation, matching cv2": Pillow's
TIFF reader rotates and cannot be told not to. Coming back upright is the
useful outcome; carrying the tag on top of it was the defect.
Diego.F
1cfdf192d8