[Geotiff] NoColor tag in GeoTiff

[Frank Warmerdam]

David,

I'm guessing that when you refer to "NoColor" this is what I normally
think of as
the NODATA value.  The GDAL tag used for this is documented on the Aware
Systems web site under private tags:

http://www.awaresystems.be/imaging/tiff/tifftags/gdal_nodata.html

The tag is define with regard to GDAL and is not part of the GeoTIFF
specification.

Best regards,

On Fri, Mar 2, 2012 at 8:20 PM, David Strip <geotiff at stripfamily.net> wrote:
> I've got some geotiffs with NoColor tags in the headers that I want to
> edit. (The nocolor tag is listed by gdalinfo)
> I use listgeo to capture the header, then strip the header with tiffcp.
> I've tried editing the resulting tiff with a variety of editors
> (including Photoshop and Windows Paint) and the the no data/no color
> areas appear light cyan in all the editors.
> I then add the geo headers back to the edited tiff using geotifcp -g.
> If I open the resulting geotiff in OpenEV, the no color pixels are now
> light cyan, not no data.
> It appears there's a NoColor tag in the geotiff that does not get copied
> by listgeo, then goes unrecognized by the various editors, and since it
> wasn't listed by listgeo, it's not restored by geotifcp.
>
> Are NoColor tags standard tiff headers?
> This website - http://www.awaresystems.be/imaging/tiff/tifftags.html -
> ostensibly lists the registered tags, and nocolor is not one of them.
> Are they unique to geotiff?
> Should listgeo/geotifcp copy/restore these?
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