PRO FXREAD, FILENAME, DATA, HEADER, P1, P2, P3, P4, P5, $
NANVALUE=NANVALUE, PROMPT=PROMPT, AVERAGE=AVERAGE, $
YSTEP=Y_STEP, NOSCALE=NOSCALE, NOUPDATE=NOUPDATE, $
ERRMSG=ERRMSG, NODATA=NODATA, COMPRESS = COMPRESS, $
EXTENSION=EXTENSION0
;+
; NAME:
; FXREAD
; Purpose :
; Read basic FITS files.
; Explanation :
; Read an image array from a disk FITS file. Optionally allows the
; user to read in only a subarray and/or every Nth pixel.
; Use :
; FXREAD, FILENAME, DATA [, HEADER [, I1, I2 [, J1, J2 ]] [, STEP]]
; Inputs :
; FILENAME = String containing the name of the file to be read.
; Opt. Inputs :
; I1,I2 = Data range to read in the first dimension. If passed, then
; HEADER must also be passed. If not passed, or set to -1,-1,
; then the entire range is read.
; J1,J2 = Data range to read in the second dimension. If passed, then
; HEADER and I1,J2 must also be passed. If not passed, or set
; to -1,-1, then the entire range is read.
; STEP = Step size to use in reading the data. If passed, then
; HEADER must also be passed. Default value is 1. Ignored if
; less than 1.
; Outputs :
; DATA = Data array to be read from the file.
; Opt. Outputs:
; HEADER = String array containing the header for the FITS file.
; Keywords :
; /COMPRESS - If this keyword is set and non-zero, then then treat
; the file as gzip compressed. By default FXREAD assumes
; the file is gzip compressed if it ends in ".gz"
; NANVALUE = Value signalling data dropout. All points corresponding to
; IEEE NaN (not-a-number) are set to this value. Ignored
; unless DATA is of type float or double-precision.
; EXTENSION = FITS extension. It can be a scalar integer,
; indicating the extension number (extension number 0
; is the primary HDU). It can also be a scalar string,
; indicating the extension name (EXTNAME keyword).
; Default: 0 (primary HDU)
; PROMPT = If set, then the optional parameters are prompted for at the
; keyboard.
; AVERAGE = If set, then the array size is reduced by averaging pixels
; together rather than by subselecting pixels. Ignored unless
; STEP is nontrivial. Note: this is much slower.
; YSTEP = If passed, then STEP is the step size in the 1st dimension,
; and YSTEP is the step size in the 2nd dimension. Otherwise,
; STEP applies to both directions.
; NOSCALE = If set, then the output data will not be scaled using the
; optional BSCALE and BZERO keywords in the FITS header.
; Default is to scale, if and only if BSCALE and BZERO are
; present and nontrivial.
; NOUPDATE = If set, then the optional BSCALE and BZERO keywords in the
; optional HEADER array will not be changed. The default is
; to reset these keywords to BSCALE=1, BZERO=0. Ignored if
; NOSCALE is set.
; ERRMSG = If defined and passed, then any error messages will be
; returned to the user in this parameter rather than
; depending on the MESSAGE routine in IDL. If no errors are
; encountered, then a null string is returned. In order to
; use this feature, ERRMSG must be defined first, e.g.
;
; ERRMSG = ''
; FXREAD, ERRMSG=ERRMSG, ...
; IF ERRMSG NE '' THEN ...
; NODATA = If set, then the array is not read in, but the
; primary header is read.
;
; Calls :
; GET_DATE, FXADDPAR, FXHREAD, FXPAR, WHERENAN
; Common :
; None.
; Restrictions:
; Groups are not supported.
;
; The optional parameters I1, I2, and STEP only work with one or
; two-dimensional arrays. J1 and J2 only work with two-dimensional
; arrays.
;
; Use of the AVERAGE keyword is not compatible with arrays with missing
; pixels.
;
; Side effects:
; If the keywords BSCALE and BZERO are present in the FITS header, and
; have non-trivial values, then the returned array DATA is formed by the
; equation
;
; DATA = BSCALE*original + BZERO
;
; However, this behavior can overridden by using the /NOSCALE keyword.
;
; If the data is scaled, then the optional HEADER array is changed so
; that BSCALE=1 and BZERO=0. This is so that these scaling parameters
; are not applied to the data a second time by another routine. Also,
; history records are added storing the original values of these
; constants. Note that only the returned array is modified--the header
; in the FITS file itself is untouched.
;
; If the /NOUPDATE keyword is set, however, then the BSCALE and BZERO
; keywords are not changed. It is then the user's responsibility to
; ensure that these parameters are not reapplied to the data. In
; particular, these keywords should not be present in any header when
; writing another FITS file, unless the user wants their values to be
; applied when the file is read back in. Otherwise, FITS readers will
; read in the wrong values for the data array.
;
; Category :
; Data Handling, I/O, FITS, Generic.
; Prev. Hist. :
; W. Thompson, May 1992, based in part on READFITS by W. Landsman, and
; STSUB by M. Greason and K. Venkatakrishna.
; W. Thompson, Jun 1992, added code to interpret BSCALE and BZERO
; records, and added NOSCALE and NOUPDATE
; keywords.
; W. Thompson, Aug 1992, changed to call FXHREAD, and to add history
; records for BZERO, BSCALE.
; Minimium IDL Version:
; V6.0 (uses V6.0 notation)
; Written :
; William Thompson, GSFC, May 1992.
; Modified :
; Version 1, William Thompson, GSFC, 12 April 1993.
; Incorporated into CDS library.
; Version 2, William Thompson, GSFC, 17 November 1993.
; Corrected bug with AVERAGE keyword on non-IEEE compatible
; machines.
; Corrected bug with subsampling on VAX machines.
; Version 3, William Thompson, GSFC, 31 May 1994
; Added ERRMSG keyword.
; Version 4, William Thompson, GSFC, 23 June 1994
; Modified so that ERRMSG is not touched if not defined.
; Version 5, Zarro (SAC/GSFC), 14 Feb 1997
; Added I/O error checking
; Version 6, 20-May-1998, David Schlegel/W. Thompson
; Allow a single pixel to be read in.
; Change the signal to read in the entire array to be -1
; Version 7 C. Markwardt 22 Sep 2003
; If the image is empty (NAXIS EQ 0), or NODATA is set, then
; return only the header.
; Version 8 W. Landsman 29 June 2004
; Added COMPRESS keyword, check for .gz extension
; Version 9, William Thompson, 19-Aug-2004
; Make sure COMPRESS is treated as a scalar
; Version 10, Craig Markwardt, 01 Mar 2004
; Add EXTENSION keyword and ability to read different
; extensions than the primary one.
; Version 11, W. Landsman September 2006
; Assume since V5.5, remove VMS support
; Version 11.1, W. Landsman November 2007
; Allow for possibility number of bytes requires 64 bit integer
; Version 12, William Thompson, 18-Jun-2010, update BLANK value.
; Version 13, W. Landsman Remove IEEE_TO_HOST, V6.0 notation
; Version 14, William Thompson, 25-Sep-2014, fix BSCALE bug in version 13
; Version 15, William Thompson, 24-Jul-2017, allow NAXISn=0 if n>NAXIS
; Version 16, W. Landsman 25-Sep-2017, allow NAXISn=0
;-
;
ON_ERROR, 2
;
; This parameter will be used later in conjunction with the average keyword.
;
ALREADY_CONVERTED = 0
READ_OK=0
;
; Parse the input parameters.
;
CASE N_PARAMS() OF
2: BEGIN & I1=-1 & I2=-1 & J1=-1 & J2=-1 & STEP=1 & END
3: BEGIN & I1=-1 & I2=-1 & J1=-1 & J2=-1 & STEP=1 & END
4: BEGIN & I1=-1 & I2=-1 & J1=-1 & J2=-1 & STEP=P1 & END
5: BEGIN & I1=P1 & I2=P2 & J1=-1 & J2=-1 & STEP=1 & END
6: BEGIN & I1=P1 & I2=P2 & J1=-1 & J2=-1 & STEP=P3 & END
7: BEGIN & I1=P1 & I2=P2 & J1=P3 & J2=P4 & STEP=1 & END
8: BEGIN & I1=P1 & I2=P2 & J1=P3 & J2=P4 & STEP=P5 & END
ELSE: BEGIN
MESSAGE = 'Syntax: FXREAD, FILENAME, DATA ' + $
'[, HEADER [, I1, I2 [, J1, J2 ] [, STEP ]]'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
END
ENDCASE
;; Extension number
IF N_ELEMENTS(EXTENSION0) EQ 0 THEN EXTENSION = 0L $
ELSE EXTENSION = EXTENSION0[0]
SZ = SIZE(EXTENSION)
ETYPE = SZ[SZ[0]+1]
IF ETYPE EQ 8 THEN BEGIN
MESSAGE = 'EXTENSION must not be a structure'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
;
; Determine if file is compressed, get the UNIT number, and open the file.
;
IF NOT KEYWORD_SET(COMPRESS) THEN $
COMPRESS = STRLOWCASE( STRMID(FILENAME, STRLEN(FILENAME)-3,3)) EQ '.gz'
OPENR, UNIT, FILENAME, /GET_LUN, ERROR=ERROR,COMPRESS=COMPRESS[0]
IF ERROR NE 0 THEN BEGIN
MESSAGE='Error opening '+FILENAME
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
;
; Read in the FITS header.
;
;; Starting extension number is zero
I_EXT = 0L
FOUND_EXT = 0
WHILE NOT FOUND_EXT DO BEGIN
FXHREAD,UNIT,HEADER,STATUS
IF STATUS NE 0 THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'Unable to read requested FITS header extension'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
;
; Extract the keywords BITPIX, NAXIS, NAXIS1, ...
;
START = 0L
BITPIX = FXPAR(HEADER,'BITPIX', START=START)
NAXIS = FXPAR(HEADER,'NAXIS', START=START)
GCOUNT = FXPAR(HEADER,'GCOUNT', START=START)
IF GCOUNT EQ 0 THEN GCOUNT = 1
PCOUNT = FXPAR(HEADER,'PCOUNT', START=START)
IF NAXIS GT 0 THEN BEGIN
DIMS = FXPAR(HEADER,'NAXIS*') ;Read dimensions
NDATA = DIMS[0]
IF NAXIS GT 1 THEN FOR I=2,NAXIS DO NDATA = NDATA*DIMS[I-1]
ENDIF ELSE NDATA = 0
NBYTES = LONG64(ABS(BITPIX) / 8) * GCOUNT * (PCOUNT + NDATA)
NREC = (NBYTES + 2879) / 2880
IF ETYPE EQ 7 THEN BEGIN
EXTNAME = STRTRIM(STRUPCASE(FXPAR(HEADER,'EXTNAME', $
START=START)),2)
IF EXTNAME EQ EXTENSION THEN FOUND_EXT = 1
END ELSE IF I_EXT EQ EXTENSION THEN FOUND_EXT = 1
IF NOT FOUND_EXT THEN BEGIN
;; Check to be sure there are extensions
IF I_EXT EQ 0 THEN BEGIN
IF NOT FXPAR(HEADER,'EXTEND', START=START) THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'Requested extension not found, and file ' + $
FILENAME + ' does not contain extensions'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
ENDIF
POINT_LUN, -UNIT, POINTLUN ;Current position
MHEAD0 = POINTLUN + NREC*2880L
POINT_LUN, UNIT, MHEAD0 ;Next FITS extension
I_EXT++
ENDIF
ENDWHILE
;;
;; If we got here, then we have arrived at the requested
;; extension. We still need to be sure that it is an image
;; and not a table (for extensions beyond the primary one,
;; that is).
;;
IF I_EXT GT 0 THEN BEGIN
XTENSION = STRTRIM(STRUPCASE(FXPAR(HEADER,'XTENSION', START=START)),2)
IF (XTENSION NE 'IMAGE') THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'Extension ' + STRTRIM(EXTENSION,2) + $
' is not an image'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
ENDIF
IF NAXIS GT 0 THEN BEGIN
DIMS = FXPAR(HEADER,'NAXIS*')
DIMS = DIMS[0:NAXIS-1]
NDATA = PRODUCT(DIMS, /INTEGER)
ENDIF ELSE NDATA = 0
;; Handle case of empty image, or no data requested
IF NDATA EQ 0 OR KEYWORD_SET(NODATA) THEN BEGIN
;; Make DATA an undefined variable, reflecting no data
DATA = 0 & DUMMY = TEMPORARY(DATA)
ERRMSG = ''
FREE_LUN,UNIT
RETURN
ENDIF
N1 = DIMS[0]
IF NAXIS EQ 2 THEN N2 = DIMS[1] ELSE N2 = 1
;
; Determine the array type from the keyword BITPIX.
;
CASE BITPIX OF
8: IDLTYPE = 1 ; Byte
16: IDLTYPE = 2 ; Integer*2
32: IDLTYPE = 3 ; Integer*4
-32: IDLTYPE = 4 ; Real*4
-64: IDLTYPE = 5 ; Real*8
ENDCASE
;
; Set the default values for the optional parameters.
;
IF (I1 EQ -1) && (I2 EQ -1) THEN BEGIN
I1 = 0
I2 = N1-1
ENDIF
IF (J1 EQ -1) && (J2 EQ -1) THEN BEGIN
J1 = 0
J2 = N2-1
ENDIF
;
; If the prompt keyword was set, the prompt for the parameters.
;
IF KEYWORD_SET(PROMPT) THEN BEGIN
ANSWER = ''
READ,'Enter lower limit for X ['+STRTRIM(I1,2)+']: ', ANSWER
IF ANSWER NE '' THEN I1 = (ANSWER)
;
ANSWER = ''
READ,'Enter upper limit for X ['+STRTRIM(I2,2)+']: ', ANSWER
IF ANSWER NE '' THEN I2 = LONG(ANSWER)
;
ANSWER = ''
READ,'Enter lower limit for Y ['+STRTRIM(J1,2)+']: ', ANSWER
IF ANSWER NE '' THEN J1 = LONG(ANSWER)
;
ANSWER = ''
READ,'Enter upper limit for Y ['+STRTRIM(J2,2)+']: ', ANSWER
IF ANSWER NE '' THEN J2 = LONG(ANSWER)
;
ANSWER = ''
READ,'Enter step size ['+STRTRIM(STEP,2)+']: ', ANSWER
IF ANSWER NE '' THEN STEP = LONG(ANSWER)
ENDIF
;
; Differentiate between XSTEP and YSTEP.
;
XSTEP = STEP > 1
IF N_ELEMENTS(Y_STEP) EQ 1 THEN YSTEP = Y_STEP ELSE YSTEP = XSTEP
;
; If any of the optional parameters were passed, then update the dimensions
; accordingly. First check I1 and I2.
;
IF (I1 NE 0) || (I2 NE N1-1) THEN BEGIN
IF NAXIS GT 2 THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'Range parameters can only be set for ' + $
'one or two-dimensional arrays'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
IF (MIN([I1,I2]) LT 0) OR (MAX([I1,I2]) GE DIMS[0]) THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'I1,I2 must be in the range 0 to ' + $
STRTRIM(DIMS[0]-1,2)
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
END ELSE IF I1 GT I2 THEN BEGIN
MESSAGE = 'I2 must be >= I1'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
DIMS[0] = I2 - I1 + 1
ENDIF
;
; Next, check J1 and J2.
;
IF (J1 NE 0) || (J2 NE N2-1) THEN BEGIN
IF NAXIS NE 2 THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'J1, J2 can only be set for ' + $
'two-dimensional arrays'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
IF (MIN([J1,J2]) LT 0) OR (MAX([J1,J2]) GE DIMS[1]) THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'J1,J2 must be in the range 0 to ' + $
STRTRIM(DIMS[1]-1,2)
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
END ELSE IF J1 GT J2 THEN BEGIN
MESSAGE = 'J2 must be >= J1'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
DIMS[1] = J2 - J1 + 1
ENDIF
;
; Next, check XSTEP. Note that the dimensions of the final result are
; somewhat differ depending on whether the keyword AVERAGE is set or not.
;
IF XSTEP GT 1 THEN BEGIN
IF NAXIS GT 2 THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'STEP can only be set for one or ' + $
'two-dimensional arrays'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
END ELSE IF XSTEP NE LONG(XSTEP) THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'STEP must be an integer value'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
END ELSE IF KEYWORD_SET(AVERAGE) THEN BEGIN
DIMS[0] = DIMS[0] / LONG(XSTEP)
END ELSE BEGIN
DIMS[0] = LONG(DIMS[0] + XSTEP - 1) / LONG(XSTEP)
INDEX = LINDGEN(DIMS[0])*XSTEP
ENDELSE
ENDIF
;
; Finally, check YSTEP. This parameter is ignored for anything other than
; two-dimensional arrays.
;
IF (NAXIS EQ 2) && (YSTEP GT 1) THEN BEGIN
IF YSTEP NE LONG(YSTEP) THEN BEGIN
FREE_LUN,UNIT
MESSAGE = 'YSTEP must be an integer value'
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
END ELSE IF KEYWORD_SET(AVERAGE) THEN BEGIN
DIMS[1] = DIMS[1] / LONG(YSTEP)
END ELSE BEGIN
DIMS[1] = LONG(DIMS[1]+YSTEP-1) / LONG(YSTEP)
ENDELSE
END ELSE YSTEP = 1
;
; Make the array.
;
DATA = MAKE_ARRAY(DIMENSION=DIMS,TYPE=IDLTYPE,/NOZERO)
;
; Find the start of the data to be read in.
;
POINT_LUN,-UNIT,OFFSET ;Current position
DELTA = N1*ABS(BITPIX)/8
IF J1 NE 0 THEN BEGIN
OFFSET = OFFSET + LONG64(J1)*DELTA
POINT_LUN,UNIT,OFFSET
ENDIF
;
; If the I range, XSTEP or YSTEP is non-trivial, then read in the file line by
; line. If pixel averaging, then read in YSTEP lines.
;
ON_IOERROR,QUIT
IF (DIMS[0] NE N1) || (XSTEP GT 1) || (YSTEP GT 1) THEN BEGIN
IF NAXIS EQ 1 THEN NJ = 1 ELSE NJ = DIMS[1]
FOR J = 0,NJ-1 DO BEGIN
IF YSTEP GT 1 THEN POINT_LUN,UNIT,OFFSET+J*YSTEP*DELTA
IF (YSTEP GT 1) && KEYWORD_SET(AVERAGE) && (NAXIS EQ 2) $
THEN LINE = MAKE_ARRAY(N1,YSTEP,TYPE=IDLTYPE,/NOZERO) $
ELSE LINE = MAKE_ARRAY(N1,TYPE=IDLTYPE,/NOZERO)
READU,UNIT,LINE
;
; If I1,I2 do not match the array size, then extract the relevant subarray.
;
IF (I1 NE 0) || (I2 NE N1-1) THEN LINE = LINE[I1:I2,*]
;
; Suppose that the step size is non-trivial. If AVERAGE was set, then convert
; to the host format, and use REBIN to average the data. (Note that missing
; pixels are not correctly handled in this case.) Otherwise, select out the
; relevant portion of the data.
;
IF (XSTEP GT 1) || (YSTEP GT 1) THEN BEGIN
IF KEYWORD_SET(AVERAGE) THEN BEGIN
SWAP_ENDIAN_INPLACE, LINE, /SWAP_IF_LITTLE
ALREADY_CONVERTED = 1
IF NAXIS EQ 1 THEN BEGIN
DATA[0,J] = REBIN(LINE[0:XSTEP*DIMS[0]]-1,DIMS[0])
END ELSE BEGIN
DATA[0,J] = REBIN(LINE[0:XSTEP*DIMS[0]-1,*],DIMS[0],1)
ENDELSE
END ELSE DATA[0,J] = LINE[INDEX]
;
; Otherwise, if the step size is trivial, then simply store the line in the
; data array.
;
END ELSE BEGIN
DATA[0,J] = LINE
ENDELSE
ENDFOR
;
; Otherwise, if the file doesn't have to be read in line by line, then just
; read the data array.
;
END ELSE READU,UNIT,DATA
;
; Convert the data from IEEE to host format, keeping track of any IEEE NaN
; values. Don't do this if the conversion has already taken place.
;
IF ~ALREADY_CONVERTED THEN BEGIN
IF (N_ELEMENTS(NANVALUE) EQ 1) && (IDLTYPE GE 4) && $
(IDLTYPE LE 6) THEN W = WHERENAN(DATA,COUNT) ELSE $
COUNT = 0
SWAP_ENDIAN_INPLACE,DATA, /SWAP_IF_LITTLE
END ELSE COUNT = 0
;
; If the parameters BZERO and BSCALE are non-trivial, then adjust the array by
; these values. Also update the BLANK keyword, if present.
;
IF ~KEYWORD_SET(NOSCALE) THEN BEGIN
BZERO = FXPAR(HEADER,'BZERO')
BSCALE = FXPAR(HEADER,'BSCALE')
BLANK = FXPAR(HEADER,'BLANK',COUNT=NBLANK)
GET_DATE,DTE
IF (BSCALE NE 0) && (BSCALE NE 1) THEN BEGIN
DATA *= BSCALE
IF ~KEYWORD_SET(NOUPDATE) THEN BEGIN
FXADDPAR,HEADER,'BSCALE',1.
FXADDPAR,HEADER,'HISTORY',DTE + $
' applied BSCALE = '+ STRTRIM(BSCALE,2)
IF NBLANK EQ 1 THEN BEGIN
print, bscale, blank
BLANK *= BSCALE
FXADDPAR,HEADER,'BLANK',BLANK
ENDIF
ENDIF
ENDIF
IF BZERO NE 0 THEN BEGIN
DATA += BZERO
IF ~KEYWORD_SET(NOUPDATE) THEN BEGIN
FXADDPAR,HEADER,'BZERO',0.
FXADDPAR,HEADER,'HISTORY',DTE + $
' applied BZERO = '+ STRTRIM(BZERO,2)
IF NBLANK EQ 1 THEN BEGIN
BLANK += BZERO
FXADDPAR,HEADER,'BLANK',BLANK
ENDIF
ENDIF
ENDIF
ENDIF
;
; Store NANVALUE everywhere where the data corresponded to IEE NaN.
;
IF COUNT GT 0 THEN DATA[W] = NANVALUE
;
; Close the file and return.
;
READ_OK=1
QUIT: ON_IOERROR,NULL
FREE_LUN, UNIT
IF NOT READ_OK THEN BEGIN
MESSAGE='Error reading file '+FILENAME
IF N_ELEMENTS(ERRMSG) NE 0 THEN BEGIN
ERRMSG = MESSAGE
RETURN
END ELSE MESSAGE, MESSAGE
ENDIF
IF N_ELEMENTS(ERRMSG) NE 0 THEN ERRMSG = ''
RETURN
END