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FITS /BITS

        [VECTOR\]FITS OutputFile.fits FROM InputFile.gdf /BITS Nbit

    The number of bits offers two controls: the data size and  the  encoding
    scheme.  This value will be found in the resulting header under the card
    BITPIX.

    Encoding scheme:
        It is controled by the Nbit sign.
        Positive sign means indexed encoding: the values are scaled as inte-
        gers  distributed  among  the  2**abs(Nbit)  values. The forward and
        back-conversion from actual values to indexed values  are  based  on
        the  data  extrema. Beware they must be up-to-date in the GDF header
        before converting a BITPIX>0 FITS (see command  V\HEADER  /EXTREMA)!
        Blank  values  are  identified  as  the  last integer of the indexed
        scale.
        Negative sign means the actual values are saved "as is" (IEEE float-
        ing point format). Blank values are saved as IEEE NaN.
    Data size:
        It  is controled by the Nbit absolute value: 16, 32, or 64 will con-
        sume respectively 2, 4 and 8 bytes per value, with a  direct  impact
        of the file size.

    Nbits=+16  is  worth  only if the data dynamic (range of values) is low,
    otherwise value precision loss will happen (2**16 values are not  enough
    to  cover  properly a large range of values). In the other cases, Nbit<0
    is more modern and should be prefered. The command supports  Nbits  +16,
    +32, -32, -64.


Gildas manager 2023-06-01