if ( as_seg ) {
    if (  ( ip.x – A.x ) * ( ip.x – B.x ) > 0
      ||  ( ip.y – A.y ) * ( ip.y – B.y ) > 0
      ||  ( ip.x – E.x ) * ( ip.x – F.x ) > 0
      ||  ( ip.y – E.y ) * ( ip.y – F.y ) > 0
    ) return null ;
}

Any idea how it works with coinciding lines that are intersecting?
I know that there might be multiple points that will intersect, but let’s assume that we only return the upper left point.

thanks a lot for this piece of code. Works perfectly

I’m using it to determine intersections during graphs display. I have to check lots of segments, thus I optimized the “as_seg” part a little. I removed Math.pow, which is quite slow, and didn’t repeat any multiplication/subtraction. I thought I might post it (approx 1.78 times faster):

if ( as_seg ) {
var n0:Number, n1:Number, n2:Number, n3:Number, n4:Number, n5:Number, n6:Number, n7:Number, v0:Number, v1:Number, vr0:Number, vr1:Number;
n0 = ip.x – p_a1.x;
n1 = ip.y – p_a1.y;
v0 = p_a0.y – p_a1.y;
vr0 = b1 * b1 + v0 * v0;
if ( n0 * n0 + n1 * n1 > vr0 ) return null;
n2 = ip.x – p_a0.x;
n3 = ip.y – p_a0.y;
if ( n2 * n2 + n3 * n3 > vr0 ) return null;
n4 = ip.x – p_b1.x;
n5 = ip.y – p_b1.y;
v1 = p_b0.y – p_b1.y;
vr1 = b2 * b2 + v1 * v1;
if ( n4 * n4 + n5 * n5 > vr1 ) return null;
n6 = ip.x – p_b0.x;
n7 = ip.y – p_b0.y;
if ( n6 * n6 + n7 * n7 > vr1 ) return null;
}

Kind regards and thanks again

I will use it under OpenCV.