Next: Data Records
Up: The Image Extension
Previous: The Image Extension
  Contents
The image extension follows the rules for required keywords in
extensions stated in section 3.3.2. The first keywords of a
FITS image extension header, through GCOUNT, must appear
consecutively in the order listed below.
- XTENSION (character) has the value
'IMAGE '
for
image extensions.
- BITPIX (integer) provides the number of bits per ``pixel''
value. The values allowed are the same as those for the primary data
array.
- NAXIS (integer) is, for an image extension, the number of
axes in the extension data array. A value
of zero is acceptable and indicates that no data are associated with
the current header. The
maximum possible value is 999. Negative values are not allowed.
- NAXIS, NAXIS
(NAXIS=0 - NAXIS1 not present)
(integer) is the number of elements along axis of the array. The
NAXIS keywords in an image extension are governed by the
same rules as those in a primary header.
- PCOUNT (integer) has the value 0 for image extensions.
- GCOUNT (integer) has the value 1 for image extensions.
(...the other keywords follow until...)
END (no value) The last keyword must be END. This
card image has no ``='' in column 9 or value field but is filled
with ASCII blanks.
The remainder of the last header record should be filled with ASCII
blanks.
Note that while the rules for generalized extensions do not specify where
the PCOUNT and GCOUNT keywords are located between the
last NAXIS and the END keywords, the image extension
rules require that they appear immediately after the last NAXIS card image.
Next: Data Records
Up: The Image Extension
Previous: The Image Extension
  Contents
William Pence
2004-01-07