Welcome to the Harris Geospatial product documentation center. Here you will find reference guides, help documents, and product libraries.


  >  Docs Center  >  Libraries  >  ASTROLIB  >  HEXTRACT

HEXTRACT

HEXTRACT

Name


      HEXTRACT

Purpose


      Extract a subimage from an array and update astrometry in FITS header

Explanation


      Extract a subimage from an array and create a new FITS header with
      updated astrometry for the subarray

Calling Sequence


      HEXTRACT, Oldim, Oldhd, [ Newim, Newhd, x0, x1, y0, y1, /SILENT ]
              or
      HEXTRACT, Oldim, Oldhd, [x0, x1, y0, y1, /SILENT, ERRMSG = ]

Inputs


      Oldim - the original image array
      Oldhd - the original image header

Optional Inputs


      x0, x1, y0, y1 - respectively, first and last X pixel, and first and
      last Y pixel to be extracted from the original image, integer scalars.
      HEXTRACT will convert these values to long integers.
      If omitted, HEXTRACT will prompt for these parameters

Optional Outputs


      Newim - the new subarray extracted from the original image
      Newhd - header for newim containing updated astrometry info
              If output parameters are not supplied or set equal to
              -1, then the HEXTRACT will modify the input parameters
              OLDIM and OLDHD to contain the subarray and updated header.

Optional Input Keyword


      ALT - Single character 'A' through 'Z' or ' ' specifying which astrometry
          system to modify in the FITS header. The default is to use the
          primary astrometry or ALT = ' '. See Greisen and Calabretta (2002)
          for information about alternate astrometry keywords.
      /SILENT - If set and non-zero, then a message describing the extraction
              is not printed at the terminal. This message can also be
              suppressed by setting !QUIET.

Optional Keyword Output


      ERRMSG - If this keyword is supplied, then any error mesasges will be
              returned to the user in this parameter rather than depending on
              on the MESSAGE routine in IDL. If no errors are encountered
              then a null string is returned.

Procedure


      The FITS header parameters NAXIS1, NAXIS2, CRPIX1, and CRPIX2 are
      updated for the extracted image.

Example


      Read an image from a FITS file 'IMAGE', extract a 512 x 512 subimage
      with the same origin, and write to a new FITS file 'IMAGENEW'
      IDL> im = READFITS( 'IMAGE', hdr ) ;Read FITS files into IDL arrays
      IDL> hextract, im, h, 0, 511, 0, 511 ;Extract 512 x 512 subimage
      IDL> writefits, 'IMAGENEW', im ,h ;Write subimage to a FITS file

Procedures Called


      CHECK_FITS, STRN(), SXPAR(), SXADDPAR, SXADDHIST

Modification History


      Written, Aug. 1986 W. Landsman, STX Corp.
      Use astrometry structure, W. Landsman Jan, 1994
      Minor fix if bad Y range supplied W. Landsman Feb, 1996
      Added /SILENT keyword W. Landsman March, 1997
      Added ERRMSG keyword W. Landsman May 2000
      Work for dimensions larger than 32767 W.L., M.Symeonidis Mar 2007
      Added ALT keyword W.L. April 2007
      Use V6.0 notation W.L. October 2012



© 2018 Harris Geospatial Solutions, Inc. |  Legal
My Account    |    Store    |    Contact Us