从python中的线段列表中检查线段的交点

如何解决从python中的线段列表中检查线段的交点

我有一个“多边形”类来显示多边形的类型，无论它是简单的（凹面还是凸面）还是复杂的。为此，我从主程序中为多边形指定的顶点创建了线段列表。 然后，我创建了“ ccw”和“ intersection”函数来检测两个线段是否相交。 现在我想要的是一个函数，该函数应该检查列表中所有线段的交点。从线段（LS）3开始的功能应检查LS 3和LS 1的交点。...然后LS 4与LS 2和LS 1的交点。然后LS 5与LS 3的交点， LS 2和LS 1等等。。。但是对于列表中的最后一个线段，它不应该检查与LS 1的交点，因为Last LS将与LS 1联接（以创建闭合多边形），并且将始终显示相交，这不是必需的。因此，对于最后一个线段，该功能应跳过与线段1的相交检查。

class Polygon:
    def __init__(self,*vertices):        
        self.vertices = [Polygon.Point(v[0],v[1]) for v in vertices] #Vertices of a polygon
    
    @property
    def lines(self):      
    #Retun list of all line segments of Polygon        
        return [Polygon.LSeg(self.vertices[i],self.vertices[(i+1)%len(self.vertices)]) for i in range(len(self.vertices))]      
    
    @property
    def shape(self):
        #THIS IS WHAT I HAVE TRIED BUT IT RETURNS "COMPLEX" FOR EVERY POLYGON#      
        for i in range(2,len(self.lines)):            
            for j in range(2,i+1):                
                if i == len(self.lines)-1 and j == i-1:                   
                   pass                
                elif self.intersect(self.lines[i],self.lines[i-j]):                    
                   return 'Complex'
    def ccw(self,A,B,C):        
         return (C.y-A.y)*(B.x-A.x) > (B.y-A.y)*(C.x-A.x)
    def intersect(self,L1,L2):
         return self.ccw(L1.p1,L2.p1,L2.p2) != self.ccw(L1.p2,L2.p2) and self.ccw(L1.p1,L1.p2,L2.p1) != self.ccw(L1.p1,L2.p2)    
    
    class LSeg:     #Line Segment Class
        def __init__(self,p1,p2):            
            self.p1=p1          
            self.p2=p2    

    class Point:       
        def __init__(self,x,y):            
            self.x=x            
            self.y=y

poly1 = Polygon((2,7),(10,1),(8,6),(11,(7,10)) #Simple Polygon

poly2 = Polygon((0.65,0.92),(-1,-3),(4,-2),(3,2),3),(6,(5,0)) #Complex Polgon  
print(poly1.shape)
print(poly2.shape)

解决方法

在下面的代码中，我添加了一个类方法，该方法检查两个LSeg是否共享一个端点。我只是使用它来避免检查具有共享端点的线段之间的交点。

请注意我的_iter_()用户

class Polygon:
    def __init__(self,*vertices):
        self.vertices = [Polygon.Point(v[0],v[1]) for v in vertices]  # Vertices of a polygon

    @property
    def lines(self):
        # Retun list of all line segments of Polygon
        return [Polygon.LSeg(self.vertices[i],self.vertices[(i + 1) % len(self.vertices)]) for i in
                range(len(self.vertices))]

    @property
    def shape(self):
        for base_line in self.lines:
            for line in self.lines:
                if not line.shares_end(base_line) and self.intersect(base_line,line):
                    return 'Complex'

    def ccw(self,A,B,C):
        return (C.y - A.y) * (B.x - A.x) > (B.y - A.y) * (C.x - A.x)

    def intersect(self,L1,L2):
        return self.ccw(L1.p1,L2.p1,L2.p2) != self.ccw(L1.p2,L2.p2) and self.ccw(L1.p1,L1.p2,L2.p1) != self.ccw(L1.p1,L2.p2)

    class LSeg:  # Line Segment Class
        def __init__(self,p1,p2):
            self.p1 = p1
            self.p2 = p2

        def __iter__(self):
            yield self.p1
            yield self.p2

        def __repr__(self):
            return f'({self.p1} | {self.p2})'

        def shares_end(self,other):
            for point in other:
                if point in self:
                    return True
            return False

    class Point:
        def __init__(self,x,y):
            self.x = x
            self.y = y

        def __repr__(self):
            return f'({self.x},{self.y})'


poly1 = Polygon((2,7),(10,1),(8,6),(11,(7,10))  # Simple Polygon

poly2 = Polygon((0.65,0.92),(-1,-3),(4,-2),(3,2),3),(6,(5,0))  # Complex Polgon
print(poly1.shape)
print(poly2.shape)

输出：

None
Complex