Oops... yes now I remember! I forgot how brilliant Astro::FITS::Header is! But
my 1990's hack worked :)
- Karl
> On 29 Apr 2017, at 9:13 pm, Craig DeForest <[email protected]> wrote:
>
> rfits and edits have two branches each: one that uses Astro::FITS::Header and
> one that doesn't. If Astro::FITS::Header is installed it *should* support
> duplicate fields and multiple lines as you want -- though there are some
> gotchas (A::F::H merges COMMENT fields into one block in the output, for
> example).
>
> A::F::H turns multiple COMMENT cards into a single multi-line string in a
> single COMMENT hash field, on read. On write the string is broken back up
> into COMMENT cards. Same for HISTORY.. You can achieve finer granularity of
> control using the non-tied interface: with A::F::H installed the hashref used
> as your PDL's header field is a pointer to the tied hash, and you can back
> out the underlying object in the usual way (with the "tied" operator).
>
> It sounds as if you might be using the legacy interface that uses Perl hashes
> alone...?
>
>
> (Mobile)
>
>> On Apr 29, 2017, at 12:54 AM, Karl Glazebrook <[email protected]> wrote:
>>
>> Yes, the FITS standard allows these particular special case duplicate
>> fields, but the PDL FITS readers has never supported them. It was done by
>> hashes and of course hashes can only have one key. I imagine to get what you
>> want you would have to modify Astro::FITS::Header either with special code
>> our to use Tie::DxHash (which is probably overkill)
>>
>> Karl
>>
>>
>>> On 29 Apr 2017, at 3:20 am, ejm <[email protected]> wrote:
>>>
>>> Hi all,
>>>
>>> I have a question about PDL::IO::FITS and in particular the methods hdr &
>>> gethdr.
>>>
>>> I've got a Moose script that works fine with PDL::IO::FITS and adds fine
>>> the usual FITS fields to a FITS
>>> header. The resulting FITS file is read fine by SAOImage and the FITS
>>> fields are in the order I want.
>>>
>>> The problem is with fields that are potential duplicates such as COMMENT
>>> and HISTORY.
>>>
>>> I noticed that PDL::IO::FITS doesn't make use of Tie::DxHash which
>>> specifically handles duplicate keys in tied hashes. Nor does
>>> Astro::FITS::Header.
>>>
>>> I also don't see exported in PDL::IO::FITS the methods insert or index from
>>> Astro::FITS::Header which might be the right methods to call for adding
>>> COMMENT fields.
>>>
>>> When I create a tied hash using Tie::DxHash and copy over the data returned
>>> by gethdr, I get a tied hash with duplicate COMMENT fields in the order I
>>> want.
>>>
>>> I then save the resultant updated FITS header hash using sethdr.
>>>
>>> But when I view the FITS file in SAOImage for example I see the added
>>> fields in alphabetical order, not the tied order they were saved in. I also
>>> don't see any COMMENT fields.
>>>
>>> If I don't use Tie::DxHash, but just add the COMMENT field directly to the
>>> tied hash returned by gethdr, I get only 1 COMMENT field in the header,
>>> with the last value assigned to it, which makes sense since Tie::DxHash
>>> isn't being used. Hence no duplicate keys allowed.
>>>
>>> What is the recommended way to add multiple COMMENT fields using
>>> PDL::IO::FITS ?
>>>
>>> Thanks,
>>>
>>> --Ed
>>>
>>>
>>>
>>>
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