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From: Frank Warmerdam <warmerdam@pobox.com>
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To: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
Cc: Andrey Kiselev <dron@ak4719.spb.edu>,
   "Tiff@Remotesensing.Org" <tiff@remotesensing.org>
Subject: Re: [Tiff] How to convert MINISBLACK to PHOTOMETRIC_RGB
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Date: Fri, 23 Jan 2004 11:44:26 -0500
X-UIDL: 4d6ddb4a8d00b457427f60ca730c0d53

Bob Friesenhahn wrote:
> On Fri, 23 Jan 2004, Frank Warmerdam wrote:
> 
> 
>>Bob Friesenhahn wrote:
>>
>>>How does this treat the two extra samples?  Does it ignore them?
>>
>>I believe that GDAL treats the 3 samples as red, green and blue in the
>>command shown by Andrey.
> 
> 
> And GraphicsMagick will only extract the primary gray channel.
> 
> 
>>PS. I don't think the Imagine generated TIFF file is so odd.  In the
>>satellite imaging community it is common for us to use MINISBLACK for
>>multispectral tiff files. The only odd part, in my mind, is the use of
>>the unspecified ExtraSamples tag.  When I see multi-sample MINISBLACK
>>TIFF files I assume that each sample should be treated as MINISBLACK with
>>no obvious pre-set RGB sample combinations.
> 
> 
> Right. MINISBLACK is pretty ordinary. The intent/meaning of the extra
> samples is undefined and may be proprietary. Perhaps they could be
> some sort of mask, or overlays which can be enabled/disabled in
> viewing software.

Bob,

They are not masks.  They are just extra MINISBLACK samples/bands/channels.
I have worked on the Imagine GeoTIFF code at times, and I don't think the
ExtraSamples stuff was meant to imply the extra bands were anything special.

I will agree that including the ExtraSamples <undefined> tag muddies the
water quite a bit.

Best regards,

-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent


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