Converts an NDF to an IRAF image NDF2IRAF
!) means no replacements are to be made. This parameter is ignored if
there are no bad values. [0] ".pix" file
contains the data array, and ".imh" is the associated header file that may contain a copy of the
NDF’s FITS extension. The suggested default is the current value. TRUE, the contents of the FITS extension of the NDF are merged with the header
information derived from the standard NDF components. See the "Notes" for details of the
merger. [TRUE] TRUE, any NDF history records are
written to the primary FITS header as HISTORY cards. These follow the mandatory headers
and any merged FITS-extension headers (see parameter PROFITS). [TRUE] a119.pix and the header file a119.imh. If there are any bad values present
they are copied verbatim to the IRAF image. a119.imh. qsospe.imh and the header file qsospe.pix. Any bad
values in the data array are replaced by zero. qsospe.imh. The NDF data array is copied to the ".pix" file. Ancillary information listed below is written to the
".imh" header file in FITS-like headers.
The IRAF “Mini World Co-ordinate System” (MWCS) is used to record axis information whenever one of the following criteria is satisfied:
The NDF title, label, units are written to the header keywords TITLE, OBJECT, and BUNIT
respectively if they are defined. Otherwise any values for these keywords found in the FITS extension
are used (provided Parameter PROFITS is TRUE). There is a limit of twenty characters for
each.
The NDF pixel origins are stored in keywords LBOUNDn for the nth dimension when any of the pixel origins is not equal to 1.
Keywords HDUCLAS1, HDUCLASn are set to "NDF" and the array-component name respectively.
The BLANK keyword is set to the Starlink standard bad value, but only for the _WORD data type and not for a quality array. It appears regardless of whether or not there are bad values actually present in the array.
HISTORY headers are propagated from the FITS extension when PROFITS is TRUE, and from the NDF
HISTORY component when PROHIS is TRUE.
If there is a FITS extension in the NDF, then the elements up to the first END keyword of this are
added to the ‘user area’ of the IRAF header file, when PROFITS=TRUE. However, certain
keywords are excluded: SIMPLE, NAXIS, NAXISn, BITPIX, EXTEND, PCOUNT, GCOUNT,
BSCALE, BZERO, END, and any already created from standard components of the NDF listed
above.
A HISTORY record is added to the IRAF header file indicating that it originated in the named NDF and was converted by NDF2IRAF.
All other NDF components are not propagated.
Some of the routines required for accessing the IRAF header image are written in SPP. Macros are used to find the start of the header line section, this constitutes an ‘Interface violation’ as these macros are not part of the IMFORT interface specification. It is possible that these may be changed in the future, so beware.
A User’s Guide to FORTRAN
Programming in IRAF, the IMFORT Interface, by Doug Tody. Only handles one-, two-, and three-dimensional NDFs.
Of the NDF’s array components only the data array may be copied.
The IRAF image produced has type SIGNED WORD or REAL dependent of the type of the NDF’s data array. (The IRAF IMFORT FORTRAN subroutine library only supports these data types.) For _BYTE, _UBYTE, and _WORD data arrays the IRAF image will have type SIGNED WORD; for all other data types of the NDF data array a REAL IRAF image is made. The pixel type of the image can be changed from within IRAF using the ‘chpixtype’ task in the ‘images’ package.
Bad values may arise due to type conversion. These too are substituted by the (non-null) value of FILLBAD.
See "Release Notes" for IRAF Version compatibility.