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1996.12.13 20:57 "Re: fillorder of decoded strips", by Sam Leffler
To: tiff@sgi.com
Subject: fillorder of decoded strips
Date: Thu, 12 Dec 1996 18:44:32 EST
From: Frank Kim <frankkim@bluejay.server.net>
Hi,
According to the documentation of TIFFOpen:
By default the library returns data in MSB2LSB bit order for
compatibiltiy with older versions of this library. Returning data in
the bit order of the native cpu makes the most sense but also requires
applications to check the value of the FillOrder tag; something they
probably do not do right now.
But according to the man page of TIFFReadEncodedStrip:
The library attempts to hide bit- and byte-ordering dif-
ferences between the image and the native machine by con-
verting data to the native machine order. Bit reversal is
done if the FillOrder tag is opposite to the native
machine bit order.
So now I'm quite confused about how TIFFReadEncodedStrip works. From a
few experiments I've done it seems the decoded data I get back from
doing a TIFFReadEncodedStrip has a fill order of MSB2LSB. Should I
assume it will always be like that as the TIFFOpen documentation
implies? Is there someway to know for sure what the fill order is of
what TIFFReadEncodedStrip returns?
Data is returned in MSB2LSB bit order unless you explicitly override
it at TIFFOpen (when samples are >1 bit). If this doesn't happen
please provide an example.
Sam