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To: John M Davison <davisonj@ecn.purdue.edu>
Cc: tiff@sgi.sgi.com
Subject: Re: TIFF Bit Ordering Versus Fill Order 
Reply-To: Sam Leffler <sam@asd.sgi.com>
In-Reply-To: Your message of "Thu, 15 Sep 1994 23:17:54 CDT."
             <199409160417.XAA10137@en.ecn.purdue.edu> 
Date: Fri, 16 Sep 1994 10:42:57 PDT
From: Sam Leffler <sam@oxford.chez.sgi.com>
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    To:  tiff@sgi.sgi.com
    Subject:  TIFF Bit Ordering Versus Fill Order
    Date: Thu, 15 Sep 1994 23:17:54 CDT
    From:  John M Davison <davisonj@ecn.purdue.edu>

            I am confused by the text on page 32 of the TIFF 6.0 Specification that
    describes the "FillOrder" tag.  In particular, let's say I had 
    
	<...stuff deleted...>
    
            What my question boils down to is this: what exactly does "FillOrder"
    mean?

FillOrder is interpreted as the order of bits in each byte of the raw
image data stored in the file.  If the bit order is different than the
host bit order then each byte of raw image data is bit-reversed before
being interpreted by a decoder.  Note that since I don't know how to
deduce the native bit order at runtime the library has the native bit
order built into it as a constant (see TIFFInitOrder in tif_open.c).

	Sam



