/// <summary>
/// 对于已有的多边形，直接将其按顶点顺序绘制出来
/// </summary>
/// <param name="polygon">多边形</param>
public void drawPolygon(CG_Polygon polygon)
{
if (polygon.nVertex < 3)
{
return;
}
Point first, prep, cur;
first = polygon.getVertex();
prep = first;
cur = polygon.getVertex();
while (cur != first)
{
drawLine_Bresenham(prep, cur, polygon.Color);
prep = cur;
cur = polygon.getVertex();
}
drawLine_Bresenham(prep, cur, polygon.Color);
}
/// <summary>
/// 双边裁剪
/// </summary>
/// <param name="target">目标多边形</param>
/// <param name="window">裁剪窗口多边形</param>
/// <returns></returns>
public CG_Polygon[] clipPolygon_WeilerAtherton(CG_Polygon target, CG_Polygon window)
{
Point t_first, t_prev, t_cur; //target
Point w_first, w_prev, w_cur; //window
Point tmp;
//将两多边形裁剪相关的成员链表清空防止之前的裁剪影响本次
if (target.clipVertex != null)
{
target.clipVertex.Clear();
}
if (window.clipVertex != null)
{
window.clipVertex.Clear();
}
if (target.intersections != null)
{
target.intersections.Clear();
}
if (window.intersections != null)
{
window.intersections.Clear();
}
target.intersections = new LinkedList <CG_Polygon.tagIntersections>();
window.intersections = new LinkedList <CG_Polygon.tagIntersections>();
//求出两多边形的交点列表
t_first = target.getVertex();
t_prev = t_first;
t_cur = target.getVertex();
do
{
bool isIn = window.isInPolygon(t_prev);//目标多边形边的始点是否在窗口内部
w_first = window.getVertex();
w_prev = w_first;
w_cur = window.getVertex();
do
{
if (Tool.isCross(t_prev, t_cur, w_prev, w_cur) == true)
{
tmp = Tool.crossPoint(t_prev, t_cur, w_prev, w_cur);
target.addIntersections(tmp, t_prev, t_cur, isIn);
window.addIntersections(tmp, w_prev, w_cur, isIn);
}
w_prev = w_cur;
w_cur = window.getVertex();
} while (w_prev != w_first);
t_prev = t_cur;
t_cur = target.getVertex();
} while (t_prev != t_first);
//将顶点加入到多边形的顶点列表中
target.setClipVertex();
window.setClipVertex();
LinkedListNode <CG_Polygon.tagClipVertex> tclip_cur = target.clipVertex.First;
LinkedListNode <CG_Polygon.tagClipVertex> wclip_cur;
while (tclip_cur != null)
{
if (tclip_cur.Value.isIntersection == true)
{
wclip_cur = window.clipVertex.First;
while (wclip_cur != null)
{
if (wclip_cur.Value.isIntersection == true && wclip_cur.Value.v == tclip_cur.Value.v)
{
CG_Polygon.tagClipVertex tmp3 = tclip_cur.Value;
LinkedListNode <CG_Polygon.tagClipVertex> prev = wclip_cur.Previous;
window.clipVertex.Remove(wclip_cur);
if (prev != null)
{
window.clipVertex.AddAfter(prev, tmp3);
}
else
{
window.clipVertex.AddFirst(tmp3);
}
break;
}
wclip_cur = wclip_cur.Next;
}
}
tclip_cur = tclip_cur.Next;
}
LinkedList <CG_Polygon> resultPolygon = new LinkedList <CG_Polygon>();//存放结果多边形的多边形列表
//开始裁剪
LinkedListNode <CG_Polygon.tagClipVertex> inter = target.findUnTracked();
//寻找一个没有被跟踪过的交点
while (inter != null)
{
CG_Polygon newPolygon = new CG_Polygon(Color.Red);
LinkedListNode <CG_Polygon.tagClipVertex> newNode = inter;
bool polygonFinish = false; //若已搜索到一个封闭多边形则为true
bool trackingTarget = true; //记录当前沿哪一个窗口边界进行跟踪
while (polygonFinish == false)
{
target.setTracked(newNode.Value.v);
window.setTracked(newNode.Value.v);
if (newPolygon.addVertex(newNode.Value.v) == false)
{
polygonFinish = true;
break;
}
if (newNode.Value.isIn == true)
{
//交点为入点，则沿目标多边形边界跟踪
newNode = target.findByPoint(newNode.Value.v);
trackingTarget = true;
}
else
{
//交点为出点，沿窗口多边形边界跟踪
newNode = window.findByPoint(newNode.Value.v);
trackingTarget = false;
}
newNode = newNode.Next;
if (newNode == null)
{
if (trackingTarget == true)
{
newNode = target.clipVertex.First;
}
else
{
newNode = window.clipVertex.First;
}
}
while (newNode != null && newNode.Value.isIntersection == false)
{
if (newPolygon.addVertex(newNode.Value.v) == true)
{
newNode = newNode.Next;
if (newNode == null)
{
if (trackingTarget == true)
{
newNode = target.clipVertex.First;
}
else
{
newNode = window.clipVertex.First;
}
}
}
else
{
polygonFinish = true;
break;
}
}
}
resultPolygon.AddLast(newPolygon);
inter = target.findUnTracked();
}
//返回结果多边形列表
if (resultPolygon.Count == 0)
{
CG_Polygon[] ret;
//无交点，结果多边形列表为空
if (window.isInPolygon(target.getFirst()) == true)
{
//目标多边形完全在裁剪窗口内部
ret = new CG_Polygon[1];
ret[0] = target;
return(ret);
}
if (target.isInPolygon(window.getFirst()) == true)
{
//裁剪窗口完全在目标多边形内部
ret = new CG_Polygon[1];
ret[0] = window;
return(ret);
}
return(null);
}
else
{
CG_Polygon[] ret = new CG_Polygon[resultPolygon.Count];
int n = resultPolygon.Count;
for (int i = 0; i < n; i++)
{
ret[i] = resultPolygon.First();
resultPolygon.RemoveFirst();
}
return(ret);
}
}