PRO rdkimg,file,headbytes,image,flag=flag,verbose=verbose,nofix=nofix
;+
; NAME:
;	RDKIMG
;	
; PURPOSE:
;       Read a KI-generated Polar Camera image file from disk and
;	return the header bytes and image.
;	
; CATEGORY:
;	
; CALLING SEQUENCE:
;	RDKIMG, FILENAME, HEADBYTES, IMAGE, FLAG=FLAG
;	
; INPUTS:
;	FILENAME: An unambiguous pathname to the image file.
;	
; KEYWORD PARAMETERS:
;       FLAG:   An optional keyword which returns 0 if the header
;               bytes and image are read successfully, and a 1
;		otherwise.
;       /VERBOSE: If set, the procedure announces exception conditions
;               and/or nonstandard actions taken.  Default is silent
;		operation.
;       /NOFIX: If set, prevents an attempt to diagnose and correct
;               a possible image problem that occurred in December
;               1994.  See notes below for a description of the
;               problem.  Default is to attempt to correct the
;		problem.
;
; OUTPUTS:
;       HEADBYTES: A 512-byte array containing the header bytes
;                  from the image.  Function GETHD converts this
;                  array to a header structure.  If an I/O error
;                  occurs while reading the file, or the file to
;                  be read is shorter than 512 bytes, or the file
;                  contains an odd number of bytes, the scalar
;		   value -1 is returned.
;       IMAGE:  An square integer array containing the image.  The
;               dimensions of the array depend on the on-chip
;               binning factors in effect at the time of image
;               acquisition.  If the routine is run on a Unix host,
;               bytes are swapped in each array element to account
;               for the endian differences between DOS and Unix.
;               If any of the error conditions mentioned above
;               occurs, or the number of bytes read from the file
;               is less than the number specified in the header,
;		the scalar value -1 is returned.
;	
; COMMON BLOCKS:
;	None.
;	
; SIDE EFFECTS:
;	None.
;
; RESTRICTIONS:
;       The file must exist.  If it exists but has been compressed
;       on the Unix side with /usr/local/bin/gzip, the routine
;       creates a temporary unzipped copy of the file and operates
;	on the copy, deleting it before returning.
;
; PROCEDURE:
;       The OS is first checked, to determine whether byte-swapping
;       will be required.  Then if the file name indicates that
;       the file has been 'gzipped', a temporary copy of the unzipped
;       file is created.  The actual reading of the file is
;       straightforward.  Byte-swapping occurs immediately after
;       reading, if needed.  If the header is present, it is decoded
;       to determine the dimensions of the image array.  If the
;       image is all there, it is cast to an INTEGER array of the
;	correct size.
;
; SEE ALSO:
;	GETHD.PRO, FIXBIN.PRO
;
; MODIFICATION HISTORY:
;	Written Jul/Aug 1992 by D P Steele.
;       Modified 93/07/07 by DPS:
;               If the file name passed ends in '.z' or '.gz', the
;               routine spawns a process to 'gunzip' the file to
;               a temporary copy, reads the copy in, and spawns
;               another process to remove the copy.  This requires
;               that the user be 'cnsr3', as all images now belong
;		to that user.
;	Modified 94/05/26 by DPS:
;		Added keyword FLAG.
;	Modified 95/01/17 by DPS:
;               If image size disagrees with header parameters but
;               is compatible with legitimate header values, header
;               is corrected and likely image flaws are remedied
;               as best they can be.  Specifically, starting on
;               941129, software binning to 4x4 was implemented,
;               incorrectly at first, with the result that a
;               4x4-binned image was overwritten over the first
;               25% of the raw 2x2 image.  The 4x4 portion is used
;               to reconstitute the top 25% of the 2x2-binned image,
;               and the header parameters are adjusted to reflect
;		the reconstituted image.
;	
;-

ON_IOERROR,bad_file

@isitdos

flag=0B

zip=(STRPOS(file,'z') EQ STRLEN(file)-1) OR $
    (STRPOS(file,'gz') EQ STRLEN(file)-2)
IF zip THEN BEGIN
    command=gzipcmd+'-d -v -c '+file+rd+'tmp'
    SPAWN,command
    sfile='tmp'
    ENDIF ELSE sfile=STRTRIM(file,2)

OPENR,unit,sfile,/GET_LUN
filestat=FSTAT(unit)

IF filestat.SIZE EQ 0 THEN BEGIN
    CLOSE,unit & FREE_LUN,unit
    MESSAGE,'No bytes found in file '+file+'; aborting',/INFORMATIONAL
    headbytes=-1
    image=-1
    flag=1B
    RETURN
    ENDIF 

in=BYTARR(filestat.SIZE)
READU,unit,in
CLOSE,unit & FREE_LUN,unit

IF zip GT 0 THEN SPAWN,rmcmd+'tmp'

IF filestat.SIZE LT 512 THEN BEGIN
    MESSAGE,'Header incomplete in file '+file+'; aborting',/INFORMATIONAL
    headbytes=-1
    image=-1
    flag=1B
    RETURN
    ENDIF 

; If an odd number of bytes was read, something is wrong
IF filestat.SIZE MOD 2 NE 0 THEN BEGIN
    MESSAGE,file+' contains an odd number of bytes; aborting',/INFORMATIONAL
    headbytes=-1
    image=-1
    flag=1B
    RETURN
    ENDIF

; Reverse byte order to put image integers in big-endian order for Unix; 
; this messes up the header, though.
IF NOT dos THEN BYTEORDER,in

headbytes=BYTE(in,0,512)	; extract header bytes
; Now put the header right, if it was reversed above.
IF NOT dos THEN BYTEORDER,headbytes

KIh=gethd(headbytes)		; decode header
cols=KIh.exp.cols/KIh.exp.sbin  ; actual # of columns in image
rows=KIh.exp.rows/KIh.exp.pbin  ; actual # of rows in image

CASE filestat.SIZE OF
512L+2L*cols*rows: BEGIN	; nominal file size found
    image=FIX(in,512,cols,rows)	; extract image bytes
    END
512L+4*2L*cols*rows: BEGIN	; image 4x expected size
    image=FIX(in,512,2*cols,2*rows)
    fixbin,headbytes,image,/top4th,verbose=verbose
    IF KEYWORD_SET(verbose) THEN $
	MESSAGE,'Image larger than expected in ' $
		+file+' - header corrected' $
	       ,/INFORMATIONAL
    END
ELSE: BEGIN
    MESSAGE,'Wrong number of bytes read from '+file,/INFORMATIONAL
    image=-1
    flag=1B
    RETURN
    END
    ENDCASE

; Special case - December 1994 images binned 4x4 were sometimes
; messed up in a way FIXBIN.PRO can correct (I hope)!
IF NOT KEYWORD_SET(nofix) THEN BEGIN
    IF (KIh.misc.dt.year EQ 1994) AND (KIH.misc.dt.month EQ 12) THEN BEGIN
        KIh=gethd(headbytes)	; make sure image parameters are up to date
        IF (KIH.exp.sbin EQ 4) AND (KIH.exp.pbin EQ 4) THEN $
	    fixbin,headbytes,image,verbose=verbose
        ENDIF
    ENDIF

RETURN

bad_file:
MESSAGE,'I/O error reading '+file,/INFORMATIONAL
headbytes=-1
image=-1
flag=1B
RETURN
END