如何判断两条直线相交

CPoint CPaintFFRDlg::Inter(int x0,int y0,int x1,int x2,int y1,int y2,int x3,int y3,int x,int y)
{
bool lim1 = false,lim2 = false;//是否垂直X轴
double k1,b1,k2,b2;//斜率和Y轴截距

//特殊情况标记
if(x1 != x0) k1 = (y1-y0)/(x1-x0),b1 = y0 - k1*x0;
else lim1 = true;
if(x3 != x2) k2 = (y3-y2)/(x3-x2),b2 = y2 - k2*x2;
else lim2 = true;

if(!lim1 && !lim2){//都不垂直于X轴
if(k1 == k2)return <a href="http://gocrazygreen.net/">HCG Diet</a> false;
x = (b2-b1)/(k1-k2);
y = k1 * x + b1;
return true;
}else if(lim1 && lim2){//2直线全垂直X轴
return false;
}else if(lim1 &&!lim2){
x = b2;
y = k2 * x + b2;
return true;
}else if(!lim1 &&lim2){
x = b1;
y = k1 * x + b1;
return CPoint (x,y);
}
return CPoint (-1,-1);

}