Automatic Conversion

Although KAPPA tasks do not work directly with `foreign' formats, they can made to appear that they do. What happens is that the format is converted `on-the-fly' to a scratch NDF, which is then processed by KAPPA. If the processing creates an output NDF or modifies the scratch NDF, this may be back-converted `on-the-fly' too, and not necessarily to the original data format. At the end, the scratch NDF is deleted. So for example you could have an IRAF image file, use BLOCK to filter the array, and output the resultant array as a FITS file.

We must first define the names of the recognised formats and a file extension associated with each format. In practice you'll most likely do this with the convert command, which creates these definitions for many popular formats. The file extension determines in which format a file is written. There is an environment variable called NDF_FORMATS_IN which defines the allowed formats in a comma-separated list with the file extensions in parentheses. Here is an example.

     % setenv NDF_FORMATS_IN 'FITS(.fit),IRAF(.imh),FIGARO(.dst)'

Once defined it lets you run KAPPA tasks on FITS, IRAF, or FIGARO files, like

     % stats m51.fit
     % stats m51.dst

would compute the statistics of a FITS file m51.fit, and then a FIGARO file m51.dst.

The environment variable also defines a search order. Had you entered

     % stats m51

STATS would first look for an NDF called m51 (stored in file m51.sdf). If it could not locate that NDF, STATS would then look for a file called m51.fit, and then m51.imh, and finally m51.dst, stopping once a file was found and associating the appropriate format with it. If none of the files exist, you'll receive a ``file not found'' error message.

You can still define an NDF section when you access an existing data file in a foreign format. Thus

     % stats m51.imh"(100:200,200~81)"

would derive the statistics for x pixels between 100 and 200, and y pixels 160 to 240 in the IRAF file m51.imh.

The conversion tasks may be your own for some private format, but normally they will come from the CONVERT package . If you want to learn how to add conversions to the standard ones, you should consult SSN/20.

There is an environment variable that defines the format of new data files. This could be assigned the same value as NDF_FORMATS_OUT, though they don't have to be.

     % setenv NDF_FORMATS_OUT 'FITS(.fit),IRAF(.imh),FIGARO(.dst)'

If you supply the file extension when a KAPPA task creates a new dataset, and it appears in NDF_FORMATS_OUT, you'll get a file in that format. So for instance,

     % ffclean in=m51.dst out=m51_cleaned.dst \\

cleans m51.dst and stores the result in m51_cleaned.dst. On the other hand, if you only give the dataset name

     % ffclean in=m51.dst out=m51_cleaned \\

the output dataset would be the first in the NDF_FORMATS_OUT list. Thus if you want to work predominantly in a foreign format, place it first in the NDF_FORMATS_IN and NDF_FORMATS_OUT lists.

If you want to create an output NDF, you must insert a full stop at the head of the list.

     % setenv NDF_FORMATS_OUT '.,FITS(.fit),IRAF(.imh),FIGARO(.dst)'

This is the recommended behaviour. If you just want to propagate the input data format, insert an asterisk at the start of the output-format list.

     % setenv NDF_FORMATS_OUT '*,.,FITS(.fit),IRAF(.imh),FIGARO(.dst)'

This only affects applications that create a dataset using information propagated from an existing dataset. For instance, if the above NDF_FORMATS_OUT were defined,

     % ffclean in=m51.dst out=m51_cleaned \\

would now create m51_cleaned.dst. If there is no propagation in the given application, the asterisk is ignored.

You can retain the scratch NDF by setting the environment variable NDF_KEEP to 1. This is useful if you intend to work mostly with NDFs and will save the conversion each time you access the dataset.

The convert command, which sets up definitions for the CONVERT package, defines the lists of input and output formats as follows.

     % setenv NDF_FORMATS_IN \
     'FITS(.fit),FIGARO(.dst),IRAF(.imh),STREAM(.das),UNFORMATTED(.unf),UNF0(.dat),
     ASCII(.asc),TEXT(.txt),GIF(.gif),TIFF(.tif),GASP(.hdr),COMPRESSED(.sdf.Z),
     GZIP(.sdf.gz),FITS(.fits),FITS(.fts),FITS(.FTS),FITS(.FITS),FITS(.FIT),
     FITS(.lilo),FITS(.lihi),FITS(.silo),FITS(.sihi),FITS(.mxlo),FITS(.rilo),
     FITS(.rihi),FITS(.vdlo),FITS(.vdhi),STREAM(.str)'

     % setenv NDF_FORMATS_OUT \
     '.,FITS(.fit),FIGARO(.dst),IRAF(.imh),STREAM(.das),UNFORMATTED(.unf),
     UNF0(.dat),ASCII(.asc),TEXT(.txt),GIF(.gif),TIFF(.tif),GASP(.hdr),
     COMPRESSED(.sdf.Z),GZIP(.sdf.gz)'

See the CONVERT documentation for more details of these conversions.