Received: from sgi.sgi.com (192.48.153.1) by cerious.com
 with SMTP (Apple Internet Mail Server 1.1.1); Fri, 14 Feb 1997 17:40:53 -0500
Received: from cthulhu.engr.sgi.com (cthulhu.engr.sgi.com [192.26.80.2]) by sgi.sgi.com (950413.SGI.8.6.12/950213.SGI.AUTOCF) via ESMTP id OAA10805; Fri, 14 Feb 1997 14:26:39 -0800
Received: (from daemon@localhost) by cthulhu.engr.sgi.com (950413.SGI.8.6.12/960327.SGI.AUTOCF) id RAA19942 for tiff-list; Fri, 14 Feb 1997 17:41:53 GMT
Received: from sgi.sgi.com (sgi.engr.sgi.com [192.26.80.37]) by cthulhu.engr.sgi.com (950413.SGI.8.6.12/960327.SGI.AUTOCF) via ESMTP id JAA19936 for <tiff-relay@relay.engr.sgi.com>; Fri, 14 Feb 1997 09:41:52 -0800
Received: from giraffe.asd.sgi.com (giraffe.asd.sgi.com [192.26.72.158]) by sgi.sgi.com (950413.SGI.8.6.12/950213.SGI.AUTOCF) via ESMTP id JAA02726 for <tiff@sgi.com>; Fri, 14 Feb 1997 09:41:52 -0800
Received: from melange.engr.sgi.com by giraffe.asd.sgi.com via ESMTP (951211.SGI.8.6.12.PATCH1502/951211.SGI)
	 id JAA10936; Fri, 14 Feb 1997 09:41:42 -0800
Received: from localhost by melange.engr.sgi.com via SMTP (940816.SGI.8.6.9/950213.SGI.AUTOCF)
	 id JAA06559; Fri, 14 Feb 1997 09:41:42 -0800
Message-Id: <199702141741.JAA06559@melange.engr.sgi.com>
X-Mailer: exmh version 2.0alpha 12/3/96
To: gabe@rfx.rfx.com (Gabe Foster)
cc: tiff@sgi.com
Subject: Re: TIFFWritedEncodedStrip behavior. 
Reply-To: Sam Leffler <sam@relay.engr.SGI.COM>
In-reply-to: Your message of "Wed, 12 Feb 1997 17:53:08 PST."
             <199702130153.RAA09893@rfx.rfx.com> 
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Date: Fri, 14 Feb 1997 09:41:40 -0800
From: Sam Leffler <sam@melange.engr.sgi.com>
Sender: owner-tiff@relay.engr.SGI.COM
Precedence: bulk
Status: R

    To:  tiff@sgi.com
    Subject:  TIFFWritedEncodedStrip behavior.
    Date: Wed, 12 Feb 1997 17:53:08 PST
    From:  gabe@rfx.rfx.com (Gabe Foster)

    Hello,
            I have a question for you about TIFFWritedEncodedStrip.  Is it 
supposed
            to be able to modify buf?  It turns out that during the prediction
            encoding step buf ends up being modified.  Is this the right 
behavior?
    
            I'm using LZW with prediction encoding on.
    
Yes.  The horizontal differencing code does modify the user data; you 
can see this easily by looking at the source code.  This is the only
encoding case that modifies input data.  BTW, you could tell this by
looking at the function prototype for TIFFWritedEncodedStrip and noting
that the image data parameter is of type tdata_t and *not* const tdata_t.

        Sam


