Return-Path: <owner-tiff@olympiakos.com>
Received: from gate7.olympiakos.com ([64.32.199.150] verified)
  by cerious.com (CommuniGate Pro SMTP 3.5.7)
  with ESMTP id 679230 for pcrews@cerious.com; Wed, 18 Dec 2002 17:00:52 -0500
Received: by gate7.olympiakos.com (Postfix, from userid 65534)
	id 0756A110B1; Wed, 18 Dec 2002 17:00:22 -0500 (EST)
Received: from localhost (localhost [127.0.0.1])
	by gate7.olympiakos.com (Postfix) with SMTP
	id E97A2110AE; Wed, 18 Dec 2002 17:00:21 -0500 (EST)
Received: by gate7.olympiakos.com (bulk_mailer v1.9); Wed, 18 Dec 2002 16:59:50 -0500
Delivered-To: tiff-outgoing@gate7.olympiakos.com
Received: by gate7.olympiakos.com (Postfix, from userid 16)
	id 95928110AC; Wed, 18 Dec 2002 16:59:50 -0500 (EST)
Delivered-To: tiff@olympiakos.com
Received: from hotmail.com (f102.law11.hotmail.com [64.4.17.102])
	by gate7.olympiakos.com (Postfix) with ESMTP id 451A311092
	for <tiff@olympiakos.com>; Wed, 18 Dec 2002 16:59:49 -0500 (EST)
Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC;
	 Wed, 18 Dec 2002 13:55:07 -0800
Received: from 193.237.112.2 by lw11fd.law11.hotmail.msn.com with HTTP;
	Wed, 18 Dec 2002 21:55:07 GMT
X-Originating-IP: [193.237.112.2]
From: "Dominic Smith" <dominicsmith501@hotmail.com>
To: leonardr@lazerware.com, tiff@olympiakos.com
Subject: Re: CMYK JPEG's
Date: Wed, 18 Dec 2002 21:55:07 +0000
Mime-Version: 1.0
Content-Type: text/plain; format=flowed
Message-ID: <F102t3V5g2oHzGkzMcv0002d272@hotmail.com>
X-OriginalArrivalTime: 18 Dec 2002 21:55:07.0725 (UTC) FILETIME=[210E0FD0:01C2A6E0]
Sender: owner-tiff@olympiakos.com
Precedence: bulk

<x-flowed>I thought this all made sense, but after some more experimenting I'm not too 
sure.

The "inverted" CMYK JPEG's I have display OK in Paintshop 7 and the Windows 
XP image viewer. OK, so maybe they are being clever and looking at the Adobe 
tag...

But when I create a CMYK JPEG from scratch using libjpeg (correct data, and 
presumably no Adobe tag) both apps show it as negative.

This makes me suspect that, rather than being clever these apps have adopted 
the Adobe polarity as a default (either deliberately or accidentally). If 
so, the situation look pretty hopeless :(

Just in case I have made a silly mistake and got everything the wrong way 
around, does anyone have a sample CMYK JPEG image which they can say for 
absolute certain is a "white-is-zero" non-Adobe tagged image?

Thanks

Dom


>From: Leonard Rosenthol <leonardr@lazerware.com>
>To: "Dominic Smith" <dominicsmith501@hotmail.com>,tiff@olympiakos.com
>Subject: Re: CMYK JPEG's
>Date: Tue, 17 Dec 2002 22:14:57 -0500
>
>At 9:47 PM +0000 12/17/02, Dominic Smith wrote:
>>I have some CMYK JPEG (.jpg, not TIFF JPEG) files which open ok in several 
>>recent PC packages (Paintshop 7 etc). But when I read them with libjpeg 
>>they are negative.
>
>	They are most likely created by Adobe software, which writes out 
>"inverted" CMYK JPEGs.  This problem is described in quite a lot of detail 
>in the libjpeg and Ghostscript documentation - check them out!
>
>
>>I read that JPEG doesn't define the polarity of CMYK data, and that both 
>>interpretations (black is zero and white is zero) exist in the wild. Does 
>>libjpeg use white is zero?
>
>	Everybody except Adobe uses "white is zero"...
>
>
>>Also, has black is zero become the de facto (de Adobe?) standard? Should I 
>>invert the libjpeg output as a matter of course, and will this cover 
>>most/virtually all images I am likely to meet?
>>
>
>	No, you need to actually check to see if the data comes from an Adobe 
>application (presence of the Adobe APP1 tag) and then switch.  HOWEVER, 
>even that isn't 100% since there are some tools that will manipulate the 
>data and leave the tags in place even if they aren't valid anymore :(.
>
>
>Leonard
>--
>---------------------------------------------------------------------------
>Leonard Rosenthol                            
><mailto:leonardr@lazerware.com>
>                      			     <http://www.lazerware.com>
>
>To subscribe or unsubscribe email tiff-request@olympiakos.com with 
>subscribe
>or unsubscribe in the email body.  Libtiff home page: 
>http://www.libtiff.org


_________________________________________________________________
MSN 8 with e-mail virus protection service: 2 months FREE* 
http://join.msn.com/?page=features/virus


To subscribe or unsubscribe email tiff-request@olympiakos.com with subscribe
or unsubscribe in the email body.  Libtiff home page: http://www.libtiff.org
</x-flowed>
