Question

MFC中怎么画带箭头的直线

Answer 1

// MFC中画带箭头的直线
void CDrawArrowDemoView::DrawArrow(CPoint p1,CPoint p2,double theta,int length)
{
	theta=3.1415926*theta/180;//转换为弧度
	double Px,Py,P1x,P1y,P2x,P2y;
	//以P2为原点得到向量P2P1（P）
	Px=p1.x-p2.x;
	Py=p1.y-p2.y;
	//向量P旋转theta角得到向量P1
	P1x=Px*cos(theta)-Py*sin(theta);
	P1y=Px*sin(theta)+Py*cos(theta);
	//向量P旋转-theta角得到向量P2
	P2x=Px*cos(-theta)-Py*sin(-theta);
	P2y=Px*sin(-theta)+Py*cos(-theta);
	//伸缩向量至制定长度
	double x1,x2;
	x1=sqrt(P1x*P1x+P1y*P1y);
	P1x=P1x*length/x1;
	P1y=P1y*length/x1;
	x2=sqrt(P2x*P2x+P2y*P2y);
	P2x=P2x*length/x2;
	P2y=P2y*length/x2;
	//平移变量到直线的末端
	P1x=P1x+p2.x;
	P1y=P1y+p2.y;
	P2x=P2x+p2.x;
	P2y=P2y+p2.y;
	CClientDC dc(this);//获取客户窗口DC
	CPen pen,pen1,*oldpen;
	pen.CreatePen(PS_SOLID, 2, RGB(0, 0, 0));
	pen1.CreatePen(PS_SOLID, 2, RGB(0, 0, 255));
	oldpen=dc.SelectObject(&pen);
	dc.MoveTo(p1.x,p1.y);
	dc.LineTo(p2.x,p2.y);
	dc.SelectObject(&pen1);
	dc.MoveTo(p2.x,p2.y);
	dc.LineTo(P1x,P1y);
	dc.MoveTo(p2.x,p2.y);
	dc.LineTo(P2x,P2y);
	dc.SelectObject(oldpen);
}

Answer 2

构造一个函数，是在startPoint,endPoint间画一条带箭头的线段：
void CTry1View::DrawLine(POINT startPoint, POINT endPoint)
{
CClientDC dc(this);
dc.MoveTo(startPoint);
dc.LineTo(endPoint);

double PI = 3.1415926;
double t=PI/4; //箭头与直线夹角
double l=0.2; //箭头边长度占直线长度的百分比

POINT arrowPoint;

arrowPoint.x = (int)(l*((startPoint.x-endPoint.x)*cos(t)-(startPoint.y-endPoint.y)*sin(t))+endPoint.x);
arrowPoint.y = (int)(l*((startPoint.x-endPoint.x)*sin(t)+(startPoint.y-endPoint.y)*cos(t))+endPoint.y);
dc.MoveTo(endPoint);
dc.LineTo(arrowPoint);

arrowPoint.x = (int)(l*((startPoint.x-endPoint.x)*cos(-t)-(startPoint.y-endPoint.y)*sin(-t))+endPoint.x);
arrowPoint.y = (int)(l*((startPoint.x-endPoint.x)*sin(-t)+(startPoint.y-endPoint.y)*cos(-t))+endPoint.y);
dc.MoveTo(endPoint);
dc.LineTo(arrowPoint);
}