LibTiff Mailing List

Interesting comments concerning RGB inputs. I assumed there were tags in the
file declaring it as a BW image at least. Or is this left to me, to call the
correct procedure to interpret BW images? Obviously, one is not interested
in directly viewing a digital elevation model encoded in a geotiff as a raw
image in Photoshop, but rather post process the file for the information it
contains. The seamless.usgs.gov web site, after you drill down to the area
of interest, allows you to open a download dialog. In that dialog box, there
is a choice to change the default data type (ArcGrid) to geotiff. I was kind
of hoping with all the experience using geotiff and remote sensing, that
someone on this list had experience using this data source. I will try and
see what GDAL can do.

Garry

> Message: 2
> Date: Sat, 17 May 2008 14:22:03 -0500 (CDT)
> From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
> Subject: Re: [Tiff] 32 bit samples
> To: Garry Petrie <garry@petries.net>
> Cc: tiff@lists.maptools.org
> Message-ID:
> 	<Pine.SOC.4.64.0805171415140.14523@freddy.simplesystems.org>
> Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
> 
> 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.
> 
> 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
> 
> Message: 3
> Date: Sun, 18 May 2008 12:59:24 +0400
> From: Andrey Kiselev <dron@ak4719.spb.edu>
> Subject: Re: [Tiff] 32 bit samples
> To: tiff@lists.maptools.org
> Message-ID: <20080518085924.GD16042@ak4719.spb.edu>
> Content-Type: text/plain; charset=us-ascii
> 
> Uor mistake is that you are trying to use RGBA interface of libtiff
> which can be used for simple images only (1-3 channels, integers, <8
> bit
> in depth). No way to read complex datasets with this API. You should
> either use a low-level libtiff API or some spicialized software which
> hides this low-level details from you. GDAL (http://www.gdal.org) will
> do it for you. Also take a look on OpenEV viewer, because Photoshop is
> not a suitable tool to deal with georeferenced images.
> 
> Best regards,
> Andrey


AWARE [SYSTEMS]		Imaging expertise for the Delphi developer
		TIFF and LibTiff Mailing List Archive
	LibTiff Mailing List TIFF and LibTiff Mailing List Archive May 2008 Previous Thread Next Thread Previous by Thread Next by Thread Previous by Date Next by Date Contact The TIFF Mailing List Homepage This list is run by Frank Warmerdam Archive maintained by AWare Systems	Thread 2008.05.19 04:51 "Re: Tiff Digest, Vol 48, Issue 6", by Garry Petrie 2008.05.19 10:36 "Re: 32 bit samples", by Gerben Vos 2008.05.19 04:51 "Re: Tiff Digest, Vol 48, Issue 6", by Garry Petrie Interesting comments concerning RGB inputs. I assumed there were tags in the file declaring it as a BW image at least. Or is this left to me, to call the correct procedure to interpret BW images? Obviously, one is not interested in directly viewing a digital elevation model encoded in a geotiff as a raw image in Photoshop, but rather post process the file for the information it contains. The seamless.usgs.gov web site, after you drill down to the area of interest, allows you to open a download dialog. In that dialog box, there is a choice to change the default data type (ArcGrid) to geotiff. I was kind of hoping with all the experience using geotiff and remote sensing, that someone on this list had experience using this data source. I will try and see what GDAL can do. Garry > Message: 2 > Date: Sat, 17 May 2008 14:22:03 -0500 (CDT) > From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> > Subject: Re: [Tiff] 32 bit samples > To: Garry Petrie <garry@petries.net> > Cc: tiff@lists.maptools.org > Message-ID: > <Pine.SOC.4.64.0805171415140.14523@freddy.simplesystems.org> > Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed > > 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. > > 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 > > Message: 3 > Date: Sun, 18 May 2008 12:59:24 +0400 > From: Andrey Kiselev <dron@ak4719.spb.edu> > Subject: Re: [Tiff] 32 bit samples > To: tiff@lists.maptools.org > Message-ID: <20080518085924.GD16042@ak4719.spb.edu> > Content-Type: text/plain; charset=us-ascii > > Uor mistake is that you are trying to use RGBA interface of libtiff > which can be used for simple images only (1-3 channels, integers, <8 > bit > in depth). No way to read complex datasets with this API. You should > either use a low-level libtiff API or some spicialized software which > hides this low-level details from you. GDAL (http://www.gdal.org) will > do it for you. Also take a look on OpenEV viewer, because Photoshop is > not a suitable tool to deal with georeferenced images. > > Best regards, > Andrey

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2008.05.19 04:51 "Re: Tiff Digest, Vol 48, Issue 6", by Garry Petrie