[Geotiff] GeoTIFFs in ArcGIS 10

[Even Rouault]

Selon Max Martinez <Max.Martinez at erdas.com>:

Running tiffinfo (utility from libtiff distribution) on your file might give you
more hints on what is going on.

> April,
>
>
>
> There are at least two possibilities.
>
>
>
> First, the mask could be a whole other image in the TIFF file. This
> image would have a NewSubfileType tag value with the second bit turned
> on. You could disable this bit (then the mask image would either be
> ignored or treated as another image in the dataset) or you could remove
> the whole mask image by relinking the IFD chain without including the
> mask IFD.
>
>
>
> The other possibility is that the mask is an additional sample included
> with the 4 band image (so the image has actually 5 samples). In this
> case the ExtraSamples tag would likely have a value of 2 for
> "Unassociated alpha data" for the sample representing the mask. If you
> changed this value to 0, the mask would possibly be treated as another
> band and you might then be able to avoid displaying it.
>
>
>
> See the TIFF spec
> <http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf>  for more
> info. You may also want to investigate the source of the images (why is
> that mask being put in there in the first place?).
>
>
>
> Max
>
>
>
> From: geotiff-bounces at lists.maptools.org
> [mailto:geotiff-bounces at lists.maptools.org] On Behalf Of April Davis
> Sent: Thursday, April 07, 2011 2:20 PM
> To: geotiff at lists.maptools.org
> Subject: [Geotiff] GeoTIFFs in ArcGIS 10
>
>
>
> All,
>
>
>
> We have recently upgraded to Esri ArcGIS 10, and have started pulling in
> 4 band (red,green,blue,IR) GeoTIFFs.  We began to see areas of "no
> data".  When looking at the image in other software platforms, we do not
> see the areas of "no data".  All the pixels have a value.  We sent an
> image to Esri technical support and they replied by stating "The tiff
> has a mask tag that ArcGIS didn't use in the past.  At ArcGIS 10.0 we
> read and apply this tag.  In this case, the tag specifies band 4 to be a
> nodata mask - any place where band 4 has the value 0 will show as
> nodata.  This is a setting on the tiff file and not in ArcGIS.  ArcGIS
> just started to honor this tag."
>
>
>
> Does anyone know what tag Esri may be referring to?  If I could figure
> out what the tag is or what exactly it specified, then I could remove
> the tag or change it.  But I am at a loss as to what to look for.
>
>
>
> Any help would be appreciated.
>
>
>
> April H. Davis, GISP
>
> GIS Analyst III
>
> Southwest Florida Water Management District
>
> Mapping and GIS Section
>
> 2379 Broad Street
>
> Brooksville, FL 34604
>
> (v): 352-796-7211 x 4216
>
> (f): 352-540-6018
>
> www.watermatters.org
>
>
>
> IMPORTANT NOTICE:  All E-mail sent to or from this address are public
> record and archived.  The Southwest Florida Water Management District
> does not allow use of District equipment and E-mail facilities for
> non-District business purposes.
>
>