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Up: 6.2 Integers
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Unsigned sixteen-bit integers can be represented in FITS files by
subtracting 32768 from each value (thus offsetting the values into the range
of a signed sixteen-bit integer) before writing them to the FITS file.
BZERO keyword (or the
TZEROn keyword in the case of binary
table columns with TFORMn = 'I') must also be included in the header
with its value set to 32768 so that FITS reading software will add this
offset to the raw values in the FITS file, thus restoring them to the
original unsigned integer values. Unsigned thirty-two-bit integers can be
represented in FITS files in a similar way by applying an offset of
2147483648 (231) to the data values.