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Re: Tiff images with "short" Palette? [message #73959 is a reply to message #73864]

Wed, 08 December 2010 05:35

Bruce Bowler
Messages: 128
Registered: September 1998

Senior Member

On Tue, 07 Dec 2010 14:21:12 -0800, Matt set fingers to keyboard and
typed:

>> Yes, I think a "color vector" is 256 elements in length whether you
>> fill 2 or 100 colors.
>
> This is the crux. Can I make a "color vector" that has a length of 2
> (or 3 or 5)?. If not, is that because of limitations with IDL, or
> because of limitations to the TIFF spec. I've given the spec a glance,
> and I can't see that the palette must be 256 colors.
>
>> Hard to say if it is against the spec, I've never read it. But I don't
>> think you are going to be able to make what you want in IDL. At least I
>> don't know any way to.
>
> Yup, so now I'm looking for alternatives.
>
>> P.S. Hard to fault ArcView for loading the color table vectors. That's
>> what I would do, too. :-(
>
> No, that's exactly right, if your palette has 256 colors, load them all.
> But I really don't want a palette with 256 colors.

From a *quick* read of http://partners.adobe.com/public/developer/en/tiff/
TIFF6.pdf, it would appear that it's more a limitation of IDL, and
depending on which section of the spec you read it might be partially a
limitation of the spec, which at one point defines the size of the color
table as 3*2^BitsPerSample (seems to say you can have whatever size table
you'd like), but in another section (specifically talking about grey scale
images) says that BitsPerSample can either be 4 or 8 and somewhere says
that the default for BitsPerSample is 1 (which is neither 4 nor 8 :-)

At this point, I'd point the "flying fickle finger of fault" mostly in the
direction of IDL.

Bruce

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[Message index]

		Re: Tiff images with "short" Palette? By: Matt[2] on Tue, 07 December 2010 14:21
		Re: Tiff images with "short" Palette? By: David Fanning on Tue, 07 December 2010 12:32
		Re: Tiff images with "short" Palette? By: Matt[2] on Tue, 07 December 2010 12:26
		Re: Tiff images with "short" Palette? By: David Fanning on Tue, 07 December 2010 12:13
		Re: Tiff images with "short" Palette? By: jeanh on Wed, 08 December 2010 07:26
		Re: Tiff images with "short" Palette? By: Bruce Bowler on Wed, 08 December 2010 05:35

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