ppplcl(3NCARG)
NAME
PPPLCL - clips a polyline against a clipping rectangle. It is intended that, eventually, there should be a better routine that will clip a polyline against an arbitrary polygon, but that routine has not yet been written.
SYNOPSIS
CALL PPPLCL (XMIN,XMAX,YMIN,YMAX,XCPL,YCPL,NCPL,RWRK,LRWK,URPF,IERR)
C-BINDING SYNOPSIS
#include <ncarg/ncargC.h>
void c_ppplcl(float xmin,
float xmax,
float ymin,
float ymax,
float *xcpl,
float *ycpl,
int ncpl,
float *rwrk,
int lwrk,
int (*urpf_)(float *xcra,
float *ycra,
int *ncra),
int *ierr)
DESCRIPTION
XMIN (an input expression of type REAL) is the X coordinate
value defining the position of the left edge of the
clipping rectangle.
XMAX (an input expression of type REAL) is the X coordinate
value defining the position of the right edge of the
clipping rectangle.
YMIN (an input expression of type REAL) is the Y coordinate
value defining the position of the bottom of the clipping
rectangle.
YMAX (an input expression of type REAL) is the Y coordinate
value defining the position of the top of the clipping
rectangle.
XCPL (an input array of type REAL) is the X coordinate array for
the polyline that is to be clipped.
YCPL (an input array of type REAL) is the Y coordinate array for
the polyline that is to be clipped.
NCPL (an input expression of type INTEGER) is the number of
points defining the input polyline (the number of
meaningful elements in each of the arrays XCPL and YCPL).
RWRK (a scratch array of type REAL) is a workspace array for
PPPLCL to use. It is divided into halves; one half is used
for X coordinates and the other half for Y coordinates.
This array doesn't have to be too big unless it is
important not to break the polyline except at the edges of
the clipping rectangle.
LRWK (an input expression of type INTEGER) is the length of the
array RWRK.
URPF is the name of a user-provided routine to process the
fragments of the polyline resulting from the clipping
process. This name must appear in an EXTERNAL statement in
the routine that calls PPPLCL and the routine itself must
have the following form:
SUBROUTINE URPF (XCRA,YCRA,NCRA)
DIMENSION XCRA(NCRA),YCRA(NCRA)
...(code to process a polyline)...
RETURN
END
Each of the arguments XCRA and YCRA is a real array,
dimensioned NCRA; the former holds the X coordinates, and
the latter the Y coordinates, of a polyline fragment.
IERR (an output variable of type INTEGER) is returned with the
value zero if no errors occurred in the execution of PPPLCL
or with a small positive value if an error did occur. The
value 1 indicates that NCPL is less than or equal to zero
and the value 2 indicates that LRWK is less than 4.
C-BINDING DESCRIPTION
The C-binding argument descriptions are the same as the FORTRAN argument descriptions.
USAGE
The FORTRAN statement CALL PPPLCL (XMIN,XMAX,YMIN,YMAX,XCPL,YCPL,NCPL,RWRK,LRWK,URPF,IERR) clips a polyline against a rectangle and delivers the portions of the polyline that fall within the rectangle, one by one, to the user- specified polyline-fragment-processing routine URPF.
EXAMPLES
Use the ncargex command to see the following relevant examples: ppex01, tppack, c_ppex01.
ACCESS
To use PPPLCL or c_ppplcl, load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in that order.
SEE ALSO
Online: polypack, ppdipo, ppditr, ppinpo, ppintr, ppppap, ppunpo, ppuntr, ncarg_cbind. Hardcopy: None.
COPYRIGHT
Copyright (C) 1987-2009 University Corporation for Atmospheric Research The use of this Software is governed by a License Agreement.
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