XISF Version 1.0 Specification - DRAFT 9

[Juan Conejero]

A new version of the XISF specification document (public draft 9) is now available online:

      http://pixinsight.com/doc/docs/XISF-1.0-spec/XISF-1.0-spec.html

You may need to refresh your browser.

The previous drafts 8 and 7.1 documents are also available for reference:

      http://pixinsight.com/doc/docs/XISF-1.0-spec-D8/XISF-1.0-spec.html
      http://pixinsight.com/doc/docs/XISF-1.0-spec-D7.1/XISF-1.0-spec.html

As always, the entire PIDoc source code of the latest version is available on our GitHub open source repositories:

      https://github.com/PixInsight/XISF-specification

Main changes:

      - Support for 128-bit scalar, complex, vector and matrix properties.

      - New Structure core element.

      - New Table core element.

      - Extensive proofreading and error corrections.

All comments, suggestions and error reports are welcome.

[sander]

Hi Juan,

I found that PixInsight does not follow the specification regarding the FITSKeyword element when converting for example a DNG or CR2 file to XISF. When the option is selected to create FITS header keywords, it writes the string and date values without the expected single quotes. When converting a FITS file into XISF it does work correctly. The upcoming update of Observatory handles this, but it would be better to fix this issue in PixInsight itself.

Thanks for the updated documents!

Sander

[Juan Conejero]

Hi Sander,

When you save a FITS file with PixInsight, the single quotes are always inserted in 'string' keyword values as required by the FITS standard (this is actually done automatically by CFITSIO). However, XISF does not require these single quotes in value attributes of FITSKeyword elements. I forgot to include this feature in the XISF specification document. Thank you for pointing this bug out, I'll modify the draft document to fix it.

[sander]

Hi Juan,

In FITS it is easy to differentiate between a numeric value, a string value and a boolean value because of the quotes.  FITSKeyword doesn't have a type attribute, so you will be loosing information by dropping the single quotes. E.g. does "T" mean "true" or the string "T". I would suggest to use the quotes, or drop them but then add a type attribute. My preference is for the keeping them, because it translates easier from/to FITS. Either way, the specification should not allow a choice.

[Juan Conejero]

OK, I'll leave Section 11.6 as it is now, since it enforces compliance with the FITS standard in FITSKeyword elements, and will try to fix the lacking single quotes in the DSLR_RAW module ASAP. I'll include also an automatic fix in the reference XISF implementation, based on simple heuristics. In this way these errors won't propagate to newly created XISF files anymore. Thank you for pointing out this issue.