Return-Path: <tiff-bounces@remotesensing.org>
Received: from xserve.flids.com (adsl-065-083-169-202.sip.mco.bellsouth.net [65.83.169.202])
        by inmx017.isp.belgacom.be (8.12.11/8.12.11/Skynet-IN-2.32) with ESMTP id j4SI1ABJ009370
        for <joris.at.lebbeke@skynet.be>; Sat, 28 May 2005 20:01:12 +0200
        (envelope-from <tiff-bounces@remotesensing.org>)
Received: from adsl-065-083-169-202.sip.mco.bellsouth.net (localhost [127.0.0.1])
	by xserve.flids.com (Postfix) with ESMTP
	id 5417325B1B4D; Sat, 28 May 2005 14:00:52 -0400 (EDT)
X-Original-To: tiff@remotesensing.org
Delivered-To: tiff@remotesensing.org
Received: from outmx014.isp.belgacom.be (outmx014.isp.belgacom.be
	[195.238.2.69])
	by xserve.flids.com (Postfix) with ESMTP id 530B925B1B21
	for <tiff@remotesensing.org>; Sat, 28 May 2005 14:00:48 -0400 (EDT)
Received: from outmx014.isp.belgacom.be (localhost [127.0.0.1])
	by outmx014.isp.belgacom.be (8.12.11/8.12.11/Skynet-OUT-2.22) with
	ESMTP id j4SI0gmS005524
	for <tiff@remotesensing.org>; Sat, 28 May 2005 20:00:42 +0200
	(envelope-from <joris.at.lebbeke@skynet.be>)
Received: from dfgrrxsknr4e (154-137.246.81.adsl.skynet.be [81.246.137.154])
	by outmx014.isp.belgacom.be (8.12.11/8.12.11/Skynet-OUT-2.22) with SMTP
	id j4SI0b81005485; Sat, 28 May 2005 20:00:37 +0200
	(envelope-from <joris.at.lebbeke@skynet.be>)
Message-ID: <000701c563af$50364e10$9a89f651@dfgrrxsknr4e>
From: "Joris" <joris.at.lebbeke@skynet.be>
To: "Jean-Yves Le Ridant" <jean-yves.leridant@culture.gouv.fr>
References: <42959EB2.000055.32635@m52.126.com><1486734063.20050526142456@culture.gouv.fr><000e01c561f3$537438c0$fda5f651@dfgrrxsknr4e>
	<1698276405.20050526161052@culture.gouv.fr>
Subject: Re: [Tiff] How to Write a tif file with compression
	=COMPRESSION_JPEG& photometric = PHOTOMETRIC_YCBCR ?
Date: Sat, 28 May 2005 20:01:40 +0200
MIME-Version: 1.0
Content-Type: text/plain;
	charset="gb2312"
Content-Transfer-Encoding: 7bit
X-Priority: 3
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook Express 6.00.2800.1437
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441
Cc: yourpattern <yourpattern@126.com>, tiff <tiff@remotesensing.org>
X-BeenThere: tiff@remotesensing.org
X-Mailman-Version: 2.1.2
Precedence: list
List-Id: TIFF and libtiff discussion  <tiff.remotesensing.org>
List-Unsubscribe: <http://xserve.flids.com/mailman/listinfo/tiff>,
	<mailto:tiff-request@remotesensing.org?subject=unsubscribe>
List-Archive: <http://xserve.flids.com/pipermail/tiff>
List-Post: <mailto:tiff@remotesensing.org>
List-Help: <mailto:tiff-request@remotesensing.org?subject=help>
List-Subscribe: <http://xserve.flids.com/mailman/listinfo/tiff>,
	<mailto:tiff-request@remotesensing.org?subject=subscribe>
Sender: tiff-bounces@remotesensing.org
Errors-To: tiff-bounces@remotesensing.org
X-UIDL: 000000000023ceae.000002ca
X-MSP-STORE: Sat, 28 May 2005 20:01:19 +0200
Status:   

Jean-Yves,

> > In my humble opinion, if a multichannel colorspace start with a brightness
> > channel, and the SamplesPerPixel value equals 1, that is a unambigious
> > situation, and may be preferable over storing grayscale as full YCbCr.
>
> Yes, but do this conform to TIFF specifications ?

I thought about this further...

Apart from including ICC profiles, our best option to communicate grayscale in a
scientifically unambigious way, is probably by using the L* component of L*a*b*.
If we were to say that Photometric=YCbCr and SamplesPerPixel=1 is not legit... I
don't think we have a legit way to store L* rasters, either.

That may be a to pragmatic argument to be convincing, but I would like to add to
that, again, that Photometric=YCbCr and SamplesPerPixel=1, or
Photometric=whateverLab and SamplesPerPixel=1 is really unambigious. I would
hesitate to write it, for now, unless people here clearly indicate they feel the
same about this as I do, but I would certainly think you'll need to be prepared
to at least read it.


Joris Van Damme
info@awaresystems.be
http://www.awaresystems.be/
Download your free TIFF tag viewer for windows here:
http://www.awaresystems.be/imaging/tiff/astifftagviewer.html

_______________________________________________
Tiff mailing list: Tiff@remotesensing.org
http://xserve.flids.com/mailman/listinfo/tiff
http://www.remotesensing.org/libtiff/
