Help for POLYSCRB

 PURPOSE:

Program "polyscrb" takes the data from a standard IBIS graphics-1 vector
input file and produces from it an output image file of polygon borders
(line segments) that are scribed (drawn) against a uniform
background.  The input file consists of the coordinates of points in
the output image that are to be connected with line segments.  The output
image that is produced forms a raster base containing polygon outlines.
Program options allow the user to specify both the data number values for the
polygon borders and the background areas.  "polyscrb" is used in conjunction
with programs "polyreg" and "polygeom" to produce a scribed image for input to
program "paint".
 EXECUTION:

The input file consists of the coordinates of sequences of points in
the output image space.  Each sequence of points is to be connected
with line segments in sequential order.  The coordinates of points
are given in floating point (REAL*4) form with the line location first,
followed by the pixel location in the line.  The program rounds 
the coordinate locations to the nearest pixel in the output image space.

The records in the input file consist of an integral number of coordinate
pairs, or in other words, an integral number of points.  Sequences of points
are packed into the records end to end and may cross record boundaries.
The end of a sequence of points can either be marked by a null point or the
end of the input file, or can be implied by means of a polygon closure option.
By default a null point is a point with the coordinates (0.0,0.0).  A null
point can be defined otherwise, though, by means of the IGNOR option.  When
a polygon closure option (EXCLOSE or APCLOSE) is used, the program saves the
coordinates of the first point in a sequence and checks if this point
occurs again exactly (EXCLOSE) or approximately (APCLOSE).  If this point
does occur again, (a closed polygon has been found, and) the sequence
ends with the second occurrence of the point.  When a polygon closure option 
is used, the program interprets either a closed polygon or a null point as
an end of sequence.

In "polyscrb", the size field does not refer to the input file, but instead
determines a window (in the output image space) which will be written
out to the output file.  The program finds the line segments or portions
of line segments that lie within the window and assigns to the pixels along
these segments the data number value for line segments (polygon borders).
All pixels in the window area that are not part of a line segment are
assigned the data number for background areas.

The output image may either be byte or halfword data.  The output
file must be allocated with AL or a similar program before
running "polyscrb".

TAE COMMAND LINE FORMAT
      The following command line formats show the major allowable forms:
      polyscrb INP=a OUT=b SIZE=(sl,ss,nl,ns) optional parameters
      polyscrb INP=a OUT=b SL=sl SS=ss NL=nl NS=ns optional parameters
      polyscrb a b (sl,ss,nl,ns) optional parameters
      
       Here 'a' represents the input file name,
       'b' represents the output image file name.
EXAMPLES

 1.   polyscrb INP=OLINES OUT=SCRIB SIZE=(600,600,100,360) 'EXCLOSE

      In this example a byte-data image is produced for the window which
      starts at line 600, pixel 600 and which is 100 lines long and 360
      pixels wide.  The program will check for polygons which close
      exactly in determining the end of sequences of points in the
      input file.

 2.   polyscrb INP=OLINES OUT=SCRIBH SIZE=(600,600,100,360) 'EXCLOSE 'HALF

      In this example a halfword-data image is produced for the same window 
      which was used in example 1.

 3.   polyscrb IN.GRA OUT.IMG  DIM=3

      In this example IN.GRA is a 3-dimensional file; the output line
      segments will have the dn values specified by the z-value of the
      initial point.  All other actions are the same.

 4.   polyscrb IN.GRA OUT.IMG  DIM=3  DN = 255

      Specifying the DN value in the case of a 3-dimensional input will
      override the z-value in the graphics file; all polygons will have
      the specified DN value.

RESTRICTIONS
1. The output image can be byte or halfword data.
2. Maximum number of samples is 500,000 per line.  The TAE/VICAR executive
   may impose further size limitations.
 OPERATION:

Because the size of output images can be larger than the size of the
program's work buffer, "polyscrb" builds the output image in strips.
Each strip contains as many (of the remaining) lines of the window area
as will fit in the work buffer.  For each strip, "polyscrb" processes each
line segment one at a time.  When a line segment intersects the strip,
the slope of the segment is used in determining exactly which pixels to
use in scribing the line.

 WRITTEN BY:             A. L. Zobrist                1 Dec 1975

 COGNIZANT PROGRAMMER:   Niles Ritter		      2 Jun 1988

 REVISION:               1                           22 Sep 1978
           AMS (CRI)     Made portable for UNIX       2 Jan 1995