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 format-
        ted/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 GREG3\IMAGE connects directly an existing 2,  3  or  4-D
        GILDAS   DATA   FORMAT   image   in   the  GREG  image  buffer.  See
        HELP GREG3\IMAGE for details.

    FITS files can also be loaded in Greg:
      - Use the VECTOR\FITS command to convert a FITS image to a GDF (Gildas
        Data Format) image that will be directly readable afterwards.
      - "on-the-fly"  automatic  conversion  from  FITS  to  GDF  format for
        GREG3\IMAGE command.
      - avoid disk-to-disk conversion by loading the FITS directly in memory
        with the command SIC\DEFINE IMAGE.
    See each command HELP for details.