Re: [netcdfgroup] [netcdf-java] Writing unsigned data to attributes

• To: Java NetCDF <netcdf-java@xxxxxxxxxxxxxxxx>, netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: Re: [netcdfgroup] [netcdf-java] Writing unsigned data to attributes
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Wed, 03 Jul 2013 15:16:58 -0600

On 7/2/2013 5:52 PM, Alex Fraser wrote:

Hi John,

Thanks for the detailed explanation.

----- Original Message -----

From: "John Caron" <caron@xxxxxxxxxxxxxxxx>
[...]
3) a valid range is applied to the underlying data, before anything
else happens. [...]

Is the same true for _FillValue? In that case I think I can use the following 
rules for unsigned variables:

  - When specifying a fill value, use the same data type
    as the variable and allow it to be written signed;
    nc4 IOSP demands this.
  - When specifying a valid range, promote the data type
    (e.g. byte -> short).

For example, the following should be equivalent:

byte Band1(y, x);
    Band1:_Unsigned = "true";
    Band1:_FillValue = -1b; // byte

byte Band2(y, x);
    Band2:_Unsigned = "true";
    Band2:valid_range = 0s, 254s; // short

Is that right?

Cheers,
Alex

Hi Alex:

Yes, that should work.

John