1 EXTRACT Extract a subset (or surset) of a GDF file
        EXTRACT

    Extracts  a  subset  of  an  input  image.   The  output  image  can  be
    larger  than  the subset; in this case the additional pixels are blanked
    if the output image is being created, unmodified if it  already  exists.
    It  works on images of any dimensions, and any subset of the input image
    can be placed anywhere in the output image.  This routine  can  also  be
    used  to build a N+P dimensional image from a set of N dimensional ones,
    by initializing the output image once with its full dimensions and  then
    placing the (subset of the) input images at the appropriate place in the
    output image.
2 Y_NAME$
        TASK\FILE "Input file name" Y_NAME$

    This is the name of the input file.
2 X_NAME$
        TASK\FILE "Output file name" X_NAME$

    This is the name of the output file.
2 BLC$
        TASK\INTEGER "Bottom left corner" BLC$[4]

    This is the position (in pixel units) of the Bottom Left Corner  of  the
    extracted part (in the input map of course).  0 means 1.
2 TRC$
        TASK\INTEGER "Top right corner" TRC$[4]

    This is the position (in pixel units) of the Top  Right  Corner  of  the
    extracted  part  (in  the input map of course).  0 means the the current
    image dimension.
2 PIXEL_IN$
        TASK\INTEGER "Position of one pixel in input image" PIXEL_IN$[4]

    This is the position of one pixel in the input map.  Together  with  the
    position  of  the  same  pixel in the output map (see PIXEL_OUT$), it is
    used to align the two maps.
2 PIXEL_OUT$
        TASK\INTEGER "Position of this pixel in output image" PIXEL_OUT$[4]

    This is the position of one pixel in the output map.  Together with  the
    position  of the same pixel in the input map (see PIXEL_IN$), it is used
    to align the two maps.
2 INITIALIZE$
        TASK\LOGICAL "Initialize output image" INITIALIZE$

    Answer .TRUE.  if you want to initialize the output map, .FALSE.  if you
    want to insert the extracted part in an existing output map.
2 X_DIM$
        TASK\INTEGER "Dimensions of output image" X_DIM$[4]

    This information is only used if you initialize the output map.   It  is
    the  total dimension of the output map.  The answer should be TRC‐BLC+1,
    unless you want to allow some extra space  for  other  data.   This  can
    occur  for  example  if you are building a cube from a set of planes.  0
    means TRC‐BLC+1.
2 BLANKOUT$
        TASK\LOGICAL "Initialize with blanking value" BLANKOUT$

    Should initializing be at the blanking value or not?
2 INITVAL$
        TASK\REAL "Initialization value" INITVAL$

    Initial value, if BLANKOUT$ is False.
1 ENDOFHELP

