NAME¶
Astro::FITS::Header::Item - A card image from a FITS header
SYNOPSIS¶
$item = new Astro::FITS::Header::Item( Card => $card );
$item = new Astro::FITS::Header::Item( Keyword => $keyword,
Value => $value,
Comment => $comment,
Type => 'int'
);
$value = $item->value();
$comment = $item->comment();
$card = $item->card();
$card = "$item";
DESCRIPTION¶
Stores information about a FITS header item (in the FITS standard these are
called
Card Images). FITS Card Images can be parsed and broken into
their component keyword, values and comments. Card Images can also be created
from its components keyword, value and comment.
METHODS¶
Constructor¶
- new
- Create a new instance. Optionally can be given a hash containing
information from a header item or the card image itself.
$item = new Astro::FITS::Header::Item( Card => $card );
$item = new Astro::FITS::Header::Item( Keyword => $keyword,
Value => $value );
The list of allowed hash keys is documented in the configure method.
Returns "undef" if the information supplied was insufficient to
generate a valid header item.
- copy
- Make a copy of an Astro::FITS::Header::Item object.
$newitem = $item->copy;
Accessor Methods¶
- keyword
- Return (or set) the value of the keyword associated with the FITS card.
$keyword = $item->keyword();
$item->keyword( $key );
When a new value is supplied any "card" in the cache is
invalidated.
Supplied value is always upper-cased.
- value
- Return (or set) the value of the value associated with the FITS card.
$value = $item->value();
$item->value( $val );
When a new value is supplied any "card" in the cache is
invalidated.
If the value is an "Astro::FITS::Header" object, the type is
automatically set to "HEADER".
- comment
- Return (or set) the value of the comment associated with the FITS card.
$comment = $item->comment();
$item->comment( $comment );
When a new value is supplied any "card" in the cache is
invalidated.
- type
- Return (or set) the value of the variable type associated with the FITS
card.
$type = $item->type();
$item->type( "INT" );
Allowed types are "LOGICAL", "INT", "FLOAT",
"STRING", "COMMENT", "HEADER" and
"UNDEF".
The special type, "HEADER", is used to specify that this item
refers to a subsidiary header (eg a header in an MEFITS file or a header
in an NDF in an HDS container). See also the "subhdrs" method in
"Astro::FITS::Header" for an alternative way of specifying a
sub-header.
The type is case-insensitive, but will always be returned up-cased.
- card
- Return (or set) the 80 character header card associated with this object.
It is created if there is no cached version.
$card = $item->card();
If a new card is supplied it will only be accepted if it is 80 characters
long or fewer. The string is padded with spaces if it is too short. No
attempt (yet) )is made to shorten the string if it is too long since that
may require a check to see if the value is a string that must be shortened
with a closing single quote. Returns "undef" on assignment
failure (else returns the supplied string).
$status = $item->card( $card );
"undef" is returned if there is insufficient information in the
object to create a new card. Can assign "undef" to clear the
cache.
This method is called automatically when attempting to stringify the object.
$card = "$item";
General Methods¶
- configure
- Configures the object from multiple pieces of information.
$item->configure( %options );
Takes a hash as argument with the following keywords:
- Card
- If supplied, the value is assumed to be a standard 80 character FITS
header card. This is sent to the "parse_card" method directly.
Takes priority over any other key.
If it is an "Astro::FITS::Header::Item" it will be copied rather
than parsed.
- Keyword
- Used to specify the keyword associated with this object.
- Value
- Used to specify the value associated with this FITS item.
- Comment
- Used to specify the comment associated with this FITS item.
- Type
- Used to specify the variable type. See the "type" method for
more details. A type will be guessed if one is not supplied. The guess may
well be wrong.
Does nothing if these keys are not supplied.
- freeze
- Method to return a blessed reference to the object so that we can store
ths object on disk using Data::Dumper module.
- parse_card
- Parse a FITS card image and store the keyword, value and comment into the
object.
($key, $val, $com) = $item->parse_card( $card );
Returns an empty list on error.
- equals
- Compares this Item with another and returns true if the keyword, value,
type and comment are all equal.
$isident = $item->equals( $item2 );
SEE ALSO¶
"Astro::FITS::Header"
COPYRIGHT¶
Copyright (C) 2008-2009 Science and Technology Facilities Council. Copyright (C)
2001-2007 Particle Physics and Astronomy Research Council. All Rights
Reserved.
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 3 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful,but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place,Suite 330, Boston, MA 02111-1307, USA
AUTHORS¶
Tim Jenness <t.jenness@jach.hawaii.edu>, Alasdair Allan
<aa@astro.ex.ac.uk>