<?php
/*------------------------------------------------------------------------------
** File: vertex.php
** Description: PHP class for a polygon vertex. Used as the base object to
** build a class of polygons.
** Version: 1.6
** Author: Brenor Brophy
** Email: brenor dot brophy at gmail dot com
** Homepage: www.brenorbrophy.com
**------------------------------------------------------------------------------
** COPYRIGHT (c) 2005-2010 BRENOR BROPHY
**
** The source code included in this package is free software; you can
** redistribute it and/or modify it under the terms of the GNU General Public
** License as published by the Free Software Foundation. This license can be
** read at:
**
** http://www.opensource.org/licenses/gpl-license.php
**
** This program is distributed in the hope that it will be useful, but WITHOUT
** ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
** FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
**------------------------------------------------------------------------------
**
** Based on the paper "Efficient Clipping of Arbitary Polygons" by Gunther
** Greiner (greiner at informatik dot uni-erlangen dot de) and Kai Hormann
** (hormann at informatik dot tu-clausthal dot de), ACM Transactions on Graphics
** 1998;17(2):71-83.
**
** Available at:
**
** http://www2.in.tu-clausthal.de/~hormann/papers/Greiner.1998.ECO.pdf
**
** Another useful site describing the algorithm and with some example
** C code by Ionel Daniel Stroe is at:
**
** http://davis.wpi.edu/~matt/courses/clipping/
**
** The algorithm is extended by Brenor Brophy to allow polygons with
** arcs between vertices.
**
** Rev History
** -----------------------------------------------------------------------------
** 1.0 08/25/2005 Initial Release
** 1.1 09/04/2005 Added software license language to header comments
** 1.2 09/07/2005 Minor fix to polygon.php - no change to this file
** 1.3 04/16/2006 Minor fix to polygon.php - no change to this file
** 1.4 03/19/2009 Minor change to comments in this file. Significant
** change to polygon.php
** 1.5 07/16/2009 No change to this file
** 1.6 15/05/2010 No change to this file
*/
class segment
{
/*------------------------------------------------------------------------------
** This class contains the information about the segments between vetrices. In
** the original algorithm these were just lines. In this extended form they
** may also be arcs. By creating a separate object for the segment and then
** referencing to it forward & backward from the two vertices it links it is
** easy to track in various directions through the polygon linked list.
*/
var $xc, $yc; // Coordinates of the center of the arc
var $d; // Direction of the arc, -1 = clockwise, +1 = anti-clockwise,
// A 0 indicates this is a line
/*
** Construct a segment
*/
function segment ($xc=0, $yc=0, $d=0)
{
$this->xc = $xc; $this->yc = $yc; $this->d = $d;
}
/*
** Return the contents of a segment
*/
function Xc () { return $this->xc ;}
function Yc () { return $this->yc ;}
function d () { return $this->d ;}
/*
** Set Xc/Yc
*/
function setXc ($xc) { $this->xc = $xc; }
function setYc ($yc) { $this->yc = $yc; }
} // end of class segment
class vertex
{
/*------------------------------------------------------------------------------
** This class is almost exactly as described in the paper by Gunter/Greiner
** with some minor additions for segments. Basically it is a node in a doubly
** linked list with a few extra control variables used by the algorithm
** for boolean operations. The only methods in the class are used to encapsulate
** the properties.
*/
var $x, $y; // Coordinates of the vertex
var $nextV, $prevV; // References to the next and previous vetices in the polygon
var $nSeg, $pSeg; // References to next & previous segments
var $nextPoly; // Reference to another polygon in a list
var $intersect; // TRUE if vertex is an intersection (with another polgon)
var $neighbor; // Ref to the corresponding intersection vertex in another polygon
var $alpha; // Intersection points relative distance from previous vertex
var $entry; // TRUE if intersection is an entry point to another polygon
// FALSE if it is an exit point
var $checked; // Boolean - TRUE if vertex has been checked
var $id; // A random ID assigned to make the vertex unique
/*
** Construct a vertex
*/
function vertex ($x, $y, $xc=0, $yc=0, $d=0,
$nextV=NULL, $prevV=NULL, $nextPoly=NULL,
$intersect = FALSE, $neighbor=NULL, $alpha=0, $entry=TRUE, $checked=FALSE)
{
$this->x = $x; $this->y = $y;
$this->nextV = $nextV; $this->prevV = $prevV; $this->nextPoly = $nextPoly;
$this->intersect = $intersect; $this->neighbor = $neighbor; $this->alpha = $alpha;
$this->entry = $entry; $this->checked = $checked;
$this->id = mt_rand(0,1000000);
/*
** Create a new segment and set a reference to it. Segments are always
** placed after the vertex
*/
$this->nSeg =& new segment ($xc, $yc, $d);
$this->pSeg = NULL;
}
/*
** Get id
*/
function id() { return $this->id; }
/*
** Get/Set x/y
*/
function X() { return $this->x; }
function setX($x) { $this->x = $x; }
function Y() { return $this->y; }
function setY($y) { $this->y = $y; }
/*
** Return contents of a segment. Default is to always return the next
** segment, unless previous is specified. The special case is where
** the vertex is an intersection, in that case the contents of the
** neighbor vertex's next or prev segment is returned. Whether next
** or previous is returned depends upon the entry value of the vertex
** This method ensures that the correct segment data is returned when
** a result polygon is being constructed.
**
** For $g Next == TRUE and Prev == FALSE
*/
function Xc ($g = TRUE)
{
if ($this->isIntersect())
{
if ($this->neighbor->isEntry())
return $this->neighbor->nSeg->Xc();
else
return $this->neighbor->pSeg->Xc();
}
else
if ($g) return $this->nSeg->Xc(); else return $this->pSeg->Xc();
}
function Yc ($g = TRUE)
{
if ($this->isIntersect())
{
if ($this->neighbor->isEntry())
return $this->neighbor->nSeg->Yc();
else
return $this->neighbor->pSeg->Yc();
}
else
if ($g) return $this->nSeg->Yc(); else return $this->pSeg->Yc();
}
function d ($g = TRUE)
{
if ($this->isIntersect())
{
if ($this->neighbor->isEntry())
return $this->neighbor->nSeg->d();
else
return (-1*$this->neighbor->pSeg->d());
}
else
if ($g) return $this->nSeg->d(); else return (-1*$this->pSeg->d());
}
/*
** Set Xc/Yc (Only for segment pointed to by Nseg)
*/
function setXc ($xc) { $this->nSeg->setXc($xc); }
function setYc ($yc) { $this->nSeg->setYc($yc); }
/*
** Set/Get the reference to the next vertex
*/
function setNext (&$nextV){ $this->nextV =& $nextV; }
function &Next (){ return $this->nextV; }
/*
** Set/Get the reference to the previous vertex
*/
function setPrev (&$prevV){ $this->prevV =& $prevV; }
function &Prev (){ return $this->prevV; }
/*
** Set/Get the reference to the next segment
*/
function setNseg (&$nSeg){ $this->nSeg =& $nSeg; }
function &Nseg (){ return $this->nSeg; }
/*
** Set/Get the reference to the previous segment
*/
function setPseg (&$pSeg){ $this->pSeg =& $pSeg; }
function &Pseg (){ return $this->pSeg; }
/*
** Set/Get reference to the next Polygon
*/
function setNextPoly (&$nextPoly){ $this->nextPoly =& $nextPoly; }
function &NextPoly (){ return $this->nextPoly; }
/*
** Set/Get reference to neighbor polygon
*/
function setNeighbor (&$neighbor){ $this->neighbor =& $neighbor; }
function &Neighbor (){ return $this->neighbor; }
/*
** Get alpha
*/
function Alpha (){ return $this->alpha; }
/*
** Test for intersection
*/
function isIntersect (){ return $this->intersect; }
/*
** Set/Test for checked flag
*/
function setChecked($check = TRUE)
{
$this->checked = $check;
if ($this->neighbor && !$this->neighbor->isChecked())
$this->neighbor->setChecked();
}
function isChecked () { return $this->checked; }
/*
** Set/Test entry
*/
function setEntry ($entry = TRUE){ $this->entry = $entry; }
function isEntry (){ return $this->entry; }
/*
** Print Vertex used for debugging
*/
function print_vertex()
{
print("(".$this->x.")(".$this->y.") ");
if ($this->nSeg->d() != 0)
print(" c(".$this->nSeg->Xc().")(".$this->nSeg->Yc().")(".$this->nSeg->d().") ");
if ($this->intersect) {
print("Intersection with alpha=".$this->alpha." ");
if ($this->entry)
print(" Entry");
else
print(" Exit");}
if ($this->checked)
print(" Checked");
else
print(" Unchecked");
print("<br>");
}
} //end of class vertex
?>
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