c# – GraphicsPath.IsClockWise()扩展方法
作者:互联网
我需要为GraphicsPath对象创建一个扩展方法,以确定GraphicsPath是顺时针还是逆时针缠绕.
像这样的东西:
public static bool IsClockwise(GraphicsPath gp)
{
bool bClockWise = false;
PointF[] pts = gp.PathPoints;
foreach (PointF pt in pts)
{
//??
}
return bClockWise;
}
注意:我只是假设我们在这里需要关于GraphicsPath中各点的foreach,但如果有更好的方法,请随时提供.
原因是因为GraphicsPath的FillMode确定相邻GraphicsPath的重叠部分是“填充”(绕组)还是“填充”(备用).但是,仅当相邻的GraphicsPath以相同的方向缠绕时才会出现这种情况.
如果两个路径以相反的方向缠绕,即使将FillMode设置为绕组也会导致(不需要的)孔.
有趣的是,GraphicsPath DOES有一个.Reverse()方法,允许人们改变路径的方向(并且这可以解决问题),但是不可能知道什么时候需要的GraphicsPath.在不知道方向的情况下反转的路径.
你能帮忙解决这个扩展方法吗?
解决方法:
我大部分都把它扔到那里因为这个问题引起了我的兴趣,这是我没有专业知识的东西,我想引发讨论.
我拿了Point in Polygon pseudo-code并试图让它适合你的情况.似乎你只对确定是顺时针还是逆时针缠绕的东西感兴趣.这是一个简单的测试和一个非常简单(粗略的边缘)C#实现.
[Test]
public void Test_DetermineWindingDirection()
{
GraphicsPath path = new GraphicsPath();
// Set up points collection
PointF[] pts = new[] {new PointF(10, 60),
new PointF(50, 110),
new PointF(90, 60)};
path.AddLines(pts);
foreach(var point in path.PathPoints)
{
Console.WriteLine("X: {0}, Y: {1}",point.X, point.Y);
}
WindingDirection windingVal = DetermineWindingDirection(path.PathPoints);
Console.WriteLine("Winding value: {0}", windingVal);
Assert.AreEqual(WindingDirection.Clockwise, windingVal);
path.Reverse();
foreach(var point in path.PathPoints)
{
Console.WriteLine("X: {0}, Y: {1}",point.X, point.Y);
}
windingVal = DetermineWindingDirection(path.PathPoints);
Console.WriteLine("Winding value: {0}", windingVal);
Assert.AreEqual(WindingDirection.CounterClockWise, windingVal);
}
public enum WindingDirection
{
Clockwise,
CounterClockWise
}
public static WindingDirection DetermineWindingDirection(PointF[] polygon)
{
// find a point in the middle
float middleX = polygon.Average(p => p.X);
float middleY = polygon.Average(p => p.Y);
var pointInPolygon = new PointF(middleX, middleY);
Console.WriteLine("MiddlePoint = {0}", pointInPolygon);
double w = 0;
var points = polygon.Select(point =>
{
var newPoint = new PointF(point.X - pointInPolygon.X, point.Y - pointInPolygon.Y);
Console.WriteLine("New Point: {0}", newPoint);
return newPoint;
}).ToList();
for (int i = 0; i < points.Count; i++)
{
var secondPoint = i + 1 == points.Count ? 0 : i + 1;
double X = points[i].X;
double Xp1 = points[secondPoint].X;
double Y = points[i].Y;
double Yp1 = points[secondPoint].Y;
if (Y * Yp1 < 0)
{
double r = X + ((Y * (Xp1 - X)) / (Y - Yp1));
if (r > 0)
if (Y < 0)
w = w + 1;
else
w = w - 1;
}
else if ((Y == 0) && (X > 0))
{
if (Yp1 > 0)
w = w + .5;
else
w = w - .5;
}
else if ((Yp1 == 0) && (Xp1 > 0))
{
if (Y < 0)
w = w + .5;
else
w = w - .5;
}
}
return w > 0 ? WindingDirection.ClockWise : WindingDirection.CounterClockwise;
}
我所提出的不同之处在于,我对你的问题有点具体,就是我计算了所有点的X和Y的平均值,并将其用作“多边形点”值.所以,传递一个点数组,它会在它们中间找到一些东西.
我还假设V i 1应该在到达points数组的边界时环绕
if (i + 1 == points.Count)
// use points[0] instead
这还没有得到优化,它只是可以回答你的问题.也许你自己已经想出了这个.
这里希望有建设性的批评.
标签:c,algorithm,methods,graphicspath 来源: https://codeday.me/bug/20190606/1189349.html