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Date: Wed, 3 Jul 2002 09:26:55 -0400
To: tiff <tiff@olympiakos.com>
From: Jon Saxton <spam.free@verizon.net>
Reply-To: Jon Saxton <js@triton.vg>
In-Reply-To: <B937CE9D.BF6C%bruno_ledoux@binuscan.com>
References: <B937CE9D.BF6C%bruno_ledoux@binuscan.com>
Subject: Photometric interpretation for grey-scale JPEG
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I had a discussion on this topic recently with another member of this mailing
list.

I encountered a bunch of JPEG-in-TIFF images which were encoded with a
Photometric Interpretation tag set to 6 (YCrCb) and it seemed to me that this
should be perfectly acceptable even though the TIFF 6.0 document says that
greyscale images should be flagged as either 0 (MINISWHITE) or 1 (MINISBLACK).

As I understand matters, the luminance component of the image can be viewed as
a greyscale image regardless of the weighting coefficients.  In other words, it
is the equivalent of an image comprising just the Y channel.

Is this correct?  If so, then should 6 be an acceptable PI for grey
JPEG-in-TIFF?

On consistency grounds, this actually seems more "correct" to me than the
recommended values.

--
Jon Saxton <js@triton.vg> OS/2 software developer
U.S. agent for Triton Technologies International Ltd
http://www.triton.vg/


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