SUBROUTINE GCON
C
C Copy a global context from an image header
C to a context file. This is the reverse of PCON. 
C
C Richard Hook, March 1999
C
      IMPLICIT NONE

      INTEGER MAXEN,MAXIM,NEN,ID
      PARAMETER (MAXEN=20000,MAXIM=1000)
      INTEGER A(MAXIM,MAXEN),ISTAT

      CHARACTER*80 CONTAB,IMAGE

C Get the name of the context table
      CALL UCLGST('contab',CONTAB,ISTAT)

C Get the name of the image containing the context 
      CALL UCLGST('image',IMAGE,ISTAT)

C Open the image with read access
      CALL UIMOPN(IMAGE,1,ID,ISTAT)
      IF(ISTAT.NE.0) THEN
         CALL UMSPUT('! Unable to open image file',1,0,ISTAT)
         GO TO 99
      ENDIF

C Read the context table from the header 
      CALL GTCOIN(ID,A,MAXIM,MAXEN,NEN,ISTAT)
      IF(ISTAT.NE.0) THEN
         CALL UMSPUT('! Unable to read context from header',
     :               1,0,ISTAT)
         GO TO 88
      ENDIF

C Write the context to the context file
      CALL PTGLCO(CONTAB,A,MAXIM,MAXEN,NEN,ISTAT)
      IF(ISTAT.NE.0) THEN
         CALL UMSPUT('! Unable to write context to file',
     :               1,0,ISTAT)
      ENDIF

 88   CONTINUE

C Close the image
      CALL UIMCLO(ID,ISTAT)

 99   CONTINUE
      RETURN
      END