判断两条线是否相交

//判断两条线段是否相交，线段1的两端坐标：point、point2  线段2的两端坐标：linePoint1、linePoint2
function isPointInLine(point,point2,linePoint1,linePoint2){
//判断两条线是否平行或者共线
    var denominator = (point.y-point2.y)*(linePoint1.x-linePoint2.x)-(point2.x-point.x)*(linePoint2.y-linePoint1.y);
    if(denominator==0)
    return false;
    //获取两条线延伸后的交点坐标
    var x = ((point.x-point2.x)*(linePoint1.x-linePoint2.x)*(linePoint2.y-point2.y)+
    (point.y-point2.y)*(linePoint1.x-linePoint2.x)*point2.x-(linePoint1.y-linePoint2.y)*(point.x-point2.x)*linePoint2.x)/denominator;
    var y = -((point.y-point2.y)*(linePoint1.y-linePoint2.y)*(linePoint2.x-point2.x)+
    (point.x-point2.x)*(linePoint1.y-linePoint2.y)*point2.y-(linePoint1.x-linePoint2.x)*(point.y-point2.y)*linePoint2.y)/denominator;
    //判断交点是否在线段上
    if((x-point2.x)*(x-point.x)<=0 && (y-point2.y)*(y-point.y)<=0 && (x-linePoint2.x)*(x-linePoint1.x)<=0 && (y-linePoint2.y)*(y-linePoint1.y)<=0)
    return {x:x,y:y}
    return false;
}
function isPointInPolygon(point,poly1){
var temppoly = poly1.split(",");
var poly = new Array();
for(var i = 0;i<temppoly.length/2;i++){
poly[i] = {x:temppoly[i*2],y:temppoly[i*2+1]};
}
    //是否点在多边形里
var re=true;
    if(poly.length>3){
    var crossNum=0;
    var point2 = {x:(poly[0].x-poly[1].x)/2,y:(poly[0].y-poly[1].y)/2}
    for(var i=1;i<poly.length;i++){
    if(i==poly.length-1){
        if(isPointInLine(point,point2,poly[i],poly[0])){
            crossNum++;
        }
    }else{
        if(isPointInLine(point,point2,poly[i],poly[i+1])){
            crossNum++;
        }
    }
    }
    if((crossNum % 2)==0){
        re=false;
    }
    }
return re;
}

评论

2 楼 zjw101018 2015-03-02  

freezingsky 写道

在平面坐标系中，测试是否是平行或者相交，直接使用斜率即可！

有木有demo，我不是很会

1 楼 freezingsky 2015-02-28  

在平面坐标系中，测试是否是平行或者相交，直接使用斜率即可！