|
private ClipPointCollection ( Point2DCollection points, |
||
| points | Point2DCollection | |
| box | ||
| return | IList |
|
private IList<Point2DCollection> ClipPointCollection(Point2DCollection points, Rectangle2D box)
{
List<Point2DCollection> list = new List<Point2DCollection>();
Rectangle2D rect = points.GetBounds();
if (((rect.Right < box.Left) || (rect.Top < box.Bottom)) || ((rect.Left > box.Right) || (rect.Bottom > box.Top)))
{
return null;
}//全部在外,不相交
if (box.Contains(rect))
{
list.Add(points);
return list;
}//全部在内
if (points.Count < 2)
{
return null;
}
Point2DCollection item = null;
bool flag = box.Contains(points[0]);
if (flag)
{
item = new Point2DCollection();
list.Add(item);
item.Add(points[0]);
}//第一个点在内
for (int i = 0; i < (points.Count - 1); i++)
{
Point2D head = points[i];
Point2D end = points[i + 1];
bool flag2 = box.Contains(end);
if (flag && flag2)
{
item.Add(end);
}//同时在内。那么else则有三种情况,head内end外，head外edn内，hean外end外
else
{
if (flag != flag2)
{
if (flag)
{
item.Add(this.ClipLineSegment(head, end, box));
}//head内end外，添加交点
else
{
item = new Point2DCollection();
list.Add(item);
item.Add(this.ClipLineSegment(head, end, box));
item.Add(end);
}//head外edn内，添加交点和end点
}
else
{
Rectangle2D segmentBox = new Rectangle2D(Math.Min(head.X, end.X), Math.Min(head.Y, end.Y), Math.Max(head.X, end.X), Math.Max(head.Y, end.Y));
if (segmentBox.IntersectsWith(box))
{
item = new Point2DCollection();
list.Add(item);
//与四条边框求交点,在中间就添加上去
Point2D point3 = EdgeIntersection(head, end, box.Left, false);
Point2D point4 = EdgeIntersection(head, end, box.Right, false);
Point2D point5 = EdgeIntersection(head, end, box.Bottom, true);
Point2D point6 = EdgeIntersection(head, end, box.Top, true);
if ((point6.X >= box.Left) && (point6.X <= box.Right))
{
item.Add(point6);
}
if ((point5.X >= box.Left) && (point5.X <= box.Right))
{
item.Add(point5);
}
if ((point4.Y >= box.Bottom) && (point4.Y <= box.Top))
{
item.Add(point4);
}
if ((point3.Y >= box.Bottom) && (point3.Y <= box.Top))
{
item.Add(point3);
}
if (item.Count < 2)
{
list.Remove(item);
}
}//hean外end外，添加两个交点
}
flag = flag2;
}
}
for (int j = list.Count - 1; j >= 0; j--)
{
Point2DCollection pts = list[j];
if (pts.Count < 2)
{
list.RemoveAt(j);
}
}
if (list.Count == 0)
{
return null;
}
return list;
}
