//Direction of line1
float dx0=x1-x0;
float dy0=y1-y0;

//Direction of line2
float dx1=x3-x2;
float dy1=y3-y2;

//Determinant
float det=dx0*dy1-dx1*dy0;

//for non-parallel lines det!=0
float s0=((x2-x0)*dy1-(y2-y0)*dx1)/det;

//s1 only needed because of line segments.
//For infinitely long lines s0 would've been enough
float s1=((y2-y0)*dx0-(x2-x0)*dy0)/det;

//for 0<=s0<=1 and 0<=s1<=1 intersection point
//is in line segment. Otherwise <0 means before start 
//point and >1 means after end point of respective line

//Intersection point
float px=dx0*s0+x0;
float py=dy0*s0+y0;

return new b2dPoint(px, py);