PLOT IMAGE_HOWTO

        There exist a number of ways to get pixels into GREG2\.
  - Read the X, Y, Z values of a Z=f(X,Y) "image", use RGDATA (if  X  and  Y
    define  a  regularly  sampled  grid)  or  RANDOM (if X and Y are "random
    points") to make a Regular Grid Map (see help GREG1\COLUMN, GREG2\RGDATA
    and GREG2\RANDOM)
  - Read a RGDATA-format file with the RGDATA command (see topic RGDATA)
  - Define a 2-D SIC variable and fill it with  values,  or  connect  a  SIC
    variable  with  an  existing  GILDAS  DATA  FORMAT (GDF) image (See HELP
    SIC\DEFINE), or use the SIC\ACCEPT command to read formatted/unformatted
    streams  of  values  and  put  them  in  a  SIC  2-D  variable (see HELP
    SIC\ACCEPT).  Then give this 2-D variable to the internal  image  buffer
    by the RGDATA Varname/VARIABLE command.
  - The command GRAPHIC\IMAGE of GRAPHIC,  which  is  a  superset  of  GREG,
    connects  directly an existing 2,3 or 4-D GILDA DATA FORMAT image in the
    GREG image buffer. Use the GRAPHIC program instead of GREG and  look  at
    HELP IMAGE.
  - GRAPHIC enable the parallel run of image-processing  programs.  Use  the
    VECTOR\RUN  FITS_GILDAS command to convert a FITS image to a GDF (Gildas
    Data Format) image that will be  directly  readable  afterwards  by  the
    GRAPHIC program.
  - The GFITS program reads FITS images and converts them to GDF format, and
    the reverse.
  - "on-the-fly" automatic conversion from FITS to GDF format for SIC\DEFINE
    IMAGE and GRAPHIC\IMAGE commands.