double xmult(double x1,double y1,double x2,double y2,double x0,double y0)
是算叉乘的
double area_triangle(double x1,double y1,double x2,double y2,double x3,double y3)
是算面积的
double dis_ptoline(double x1,double y1,double x2,double y2,double ex,double ey,double *px,double *py)
自己编的 算点到线段距离的
double xmult(double x1,double y1,double x2,double y2,double x0,double y0)
{
return (x1-x0)*(y2-y0)-(x2-x0)*(y1-y0);
}
double area_triangle(double x1,double y1,double x2,double y2,double x3,double y3){
return fabs(xmult(x1,y1,x2,y2,x3,y3))/2;
}
double dis_ptoline(double x1,double y1,double x2,double y2,double ex,double ey,double *px,double *py)
{ //第一个点，第二个点，目标点 ax ay为答案点 返回距离
double k,b,dis,tem1,tem2,t1,t2,yd=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
t2=sqrt((x2-ex)*(x2-ex)+(y2-ey)*(y2-ey));
t1=sqrt((x1-ex)*(x1-ex)+(y1-ey)*(y1-ey));
dis=area_triangle(x1,y1,x2,y2,ex,ey)*2/yd;
tem1=sqrt(t1*t1-dis*dis);
tem2=sqrt(t2*t2-dis*dis);
if (tem1>yd||tem2>yd) {
if (t1>t2) {*px=x2;*py=y2;return t2;}
else {*px=x1;*py=y1;return t1;}
}
*px=x1+(x2-x1)*tem1/yd;
*py=y1+(y2-y1)*tem1/yd;
return dis;
}