平面坐標系中，求點在線上的投影坐標（如圖）

已知點A(x1,y1)、B(x2,y2)、M(m,n)，求點M在線段AB上的投影坐標。

 

double CTrackLineView::PointToXianDuanChuiYingPointjingdu(double m, double n, double x1, double y1, double x2, double y2)
{//計算點到線垂影坐標
	return 
		(
		(m*(x2-x1)*(x2-x1)+n*(y2-y1)*(x2-x1)+(x1*y2-x2*y1)*(y2-y1))
		/((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1))
		);


}
double CTrackLineView::PointToXianDuanChuiYingPointweidu(double m, double n, double x1, double y1, double x2, double y2)
{//計算點到線垂影坐標
	return
	(
		(m*(x2-x1)*(y2-y1)+n*(y2-y1)*(y2-y1)+(x2*y1-x1*y2)*(x2-x1))
		/((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1))
	);

}