Function segSegInt

deps/opencv/modules/imgproc/src/geometry.cpp:392–430

--------------------------------------------------------------------- segSegInt: Finds the point of intersection p between two closed segments ab and cd. Returns p and a char with the following meaning: 'e': The segments collinearly overlap, sharing a point. 'v': An endpoint (vertex) of one segment is on the other segment, but 'e' doesn't hold. '1': The segments intersect properly (i.e., they sha

// of each, returns 'e' rather than 'v' as one might expect.
//---------------------------------------------------------------------
static char segSegInt( Point2f a, Point2f b, Point2f c, Point2f d, Point2f& p, Point2f& q )
{
    double  s, t;       // The two parameters of the parametric eqns.
    double num, denom;  // Numerator and denoninator of equations.
    char code = '?';    // Return char characterizing intersection.

    denom = a.x * (double)( d.y - c.y ) +
    b.x * (double)( c.y - d.y ) +
    d.x * (double)( b.y - a.y ) +
    c.x * (double)( a.y - b.y );

    // If denom is zero, then segments are parallel: handle separately.
    if (denom == 0.0)
        return parallelInt(a, b, c, d, p, q);

    num =    a.x * (double)( d.y - c.y ) +
    c.x * (double)( a.y - d.y ) +
    d.x * (double)( c.y - a.y );
    if ( (num == 0.0) || (num == denom) ) code = 'v';
    s = num / denom;

    num = -( a.x * (double)( c.y - b.y ) +
            b.x * (double)( a.y - c.y ) +
            c.x * (double)( b.y - a.y ) );
    if ( (num == 0.0) || (num == denom) ) code = 'v';
    t = num / denom;

    if      ( (0.0 < s) && (s < 1.0) &&
             (0.0 < t) && (t < 1.0) )
        code = '1';
    else if ( (0.0 > s) || (s > 1.0) ||
             (0.0 > t) || (t > 1.0) )
        code = '0';

    p.x = (float)(a.x + s*(b.x - a.x));
    p.y = (float)(a.y + s*(b.y - a.y));

    return code;
}

static tInFlag inOut( Point2f p, tInFlag inflag, int aHB, int bHA, Point2f*& result )
{