.help impkw Sep86 imfort
.ih
NAME
impkw -- set the value of an image header keyword
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SYNOPSIS
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subroutine impkwb (im, keyw, bval, ier)
subroutine impkwc (im, keyw, cval, ier)
subroutine impkwi (im, keyw, ival, ier)
subroutine impkwr (im, keyw, rval, ier)
subroutine impkwd (im, keyw, dval, ier)

integer		im		#I image descriptor of open image
character*(*)	keyw		#I name of the keyword to be set
integer		ier		#O status return

logical		bval		#I logical (boolean) keyword value
character*(*)	cval		#I character string keyword value
integer		ival		#I integer keyword value
real		rval		#I real keyword value
doubleprecision	dval		#I double precision keyword value
.fi
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DESCRIPTION
The \fIimpkw\fR procedures are used to set the values of existing image
header keywords.  It is an error if the named keyword does not already
exist; the \fIimakw\fR procedures should be used if one wants the keyword
to be automatically added if not found, but if the keyword is known
to exist it is preferable to use the \fIimpkw\fR procedures since they
are more efficient and will detect misspelled keyword names and foreign
images.  Automatic datatype conversion is provided, i.e., it is not
necessary to know the exact datatype of a keyword to update its value.
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RETURN VALUE
A zero status is returned if the named keyword exists, is writable, and if
the datatype coercion implied is permissible.

.nf
SYS_IDBKEYNF:	image header keyword not found
SYS_IDBTYPE:	illegal header parameter data type conversion
.fi
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NOTES
It is not an error to update the value of a keyword in an image opened
for read-only access, but an error status will be returned at \fIimclos\fR or
\fIimflsh\fR time since the header cannot be updated on disk.
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SEE ALSO
imacck, imakw, imgkw
.endhelp
