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Date: Sat, 17 May 2008 14:22:03 -0500 (CDT)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: Garry Petrie <garry@petries.net>
Subject: Re: [Tiff] 32 bit samples
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Status:   

On Sat, 17 May 2008, Garry Petrie wrote:

> Resend my question. Guess this list only likes plain text?

We saw your original message, but of course plain text is better.

Hopefully you did not expect to be peppered with 1000 response emails 
from all the people who do NOT have experience with 
http://seamless.usgs.gov/website/seamless/viewer.htm? :-)

An application using libtiff can use it to retrieve 32 bit float 
samples.  The problem is that 32 bit samples can represent almost 
anything and there is no one way to create a pleasing 8bit/sample RGB 
image from it.  It is up to the application to decide what to do with 
the data.

The GDAL package (http://www.gdal.org/) is likely capable of dealing 
with these files, but I have no experience with GDAL so I can't say.

My own software (GraphicsMagick, http://www.GraphicsMagick.org/) can 
read floating-point TIFF files but it may require some user direction 
in order to obtain reasonable results.

I did not know how to use the seamless.usgs.gov site.  I did download 
a bundle of large files but did not find any TIFF files therein.

Bob

>
> From: Garry Petrie [mailto:garry@petries.net]
> Sent: Friday, May 16, 2008 2:25 PM
> To: 'tiff@lists.maptools.org'
> Subject: 32 bit samples
>
> I was wondering if anyone has experience with
>
> http://seamless.usgs.gov/website/seamless/viewer.htm
>
> This web app can produce geotiff files containing digital elevation data for
> any place in the world using data from the space shuttle SAR mission. The
> format of the tiff portion of the file contains 32 bit samples, not sure if
> they are longs or short floats. Using libtiff I get the message about not
> being able to handle 32bit samples from getimage. I know the web site
> produces good image files, as I have been able to view the files with
> AdobePS. I peaked at alpha 4.0 and it seems to have the same critical code
> as 3.8.2. Are there great obstacles in enabling this function? I am willing
> to spend some time with the code, but I don't want to become an expert.
>
> gp
>
>
>
> _______________________________________________
> Tiff mailing list: Tiff@lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/tiff
> http://www.remotesensing.org/libtiff/
>

======================================
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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