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May 2002
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2002.05.13 21:36 "Re: Fwd: Re: tsmAPI and LibTIFF", by Peter Nielsen
They definitely don't do this right. The TIFF orientation is for the image
as a whole. It is NOT strip or tile specific. If it was, then this concept
would also apply to multi-strip images (!) and we would need strip/tile
specific processing.
"JPEG assumes a top-left origin and so any TIFF viewer will flip each tile"
This is not correct thinking. This statement applies to a JFIF image as a
whole. We must not apply this thinking on partial ("raw") JPEG data.
Note that the statement also implies that the image is always stored
consequtivelty from row 0 to row N. This part of the statement is true and
is also quite relevant for strip/tile storage! Unfortunately, their
implementation does not follow this. They have implemented an ordering
where the rows no longer appear consequtivelty (4321|8765|...). The row and
column order ordering for strips and tiles should always be (1234|5678|...)
or (...|8765|4321).
Think of it like this: The TIFF data stream defines a two dimensional image
[0..X, 0..Y]. The TIFF orientation only tells where the origin [0,0] is
placed! That's all it does. It should not cause any inter-strip or inter-
tile changes.
Best regards,
Peter Nielsen