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[CF-metadata] Adding palettes to the data

From: Mike Grant <mggr>
Date: Tue, 23 Oct 2012 18:59:35 +0100

On 28/09/12 12:40, Martin Raspaud wrote:
> Within this context, we would like to associate a palette of (rgb)
..
> However, I can't find information on how to do this in netcdf and more
> particularly within CF.

This is really a presentation issue and, as such, I don't think it's
been addressed within CF, which is more about describing the data.
Similarly, the netcdf format is about containing and describing data,
rather than pictures, which would be considered as a rendering of the
data by a separate program. So I don't think you'll find anything
dealing with it in CF or netcdf docs at present.

Mark's question regarding the encoding of your data is very relevant -
are your data values already crunched down to a 0-255 range suitable for
palettising (in which case make sure you include the descaling
parameters! [1]) or are they real data of some kind?

The only other things I'd add to Mark's suggestions are that you might
want to use the "ancillary_variables" attribute [2] to link to the
"recommended" palette, and to consider the CF cell boundaries [3] as one
way of encoding ranges (this might not make sense!)

Cheers,

Mike.

[1]
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/ch08.html#packed-data
[2] http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/ch03s04.html
[3] http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/ch07.html

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Received on Tue Oct 23 2012 - 11:59:35 BST

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