public static float getXAtY(LineSegment seg, int y)
{
PointF fx = getFxForm(seg);
return((y - fx.Y) / fx.X);
}
public static bool FindIntersectionPoint(LineSegment segA, LineSegment segB, out Point result)
{
result = new Point();
bool isAV = (segA.start.X == segA.end.X);
bool isAH = (segA.start.Y == segA.end.Y);
bool isBV = (segB.start.X == segB.end.X);
bool isBH = (segB.start.Y == segB.end.Y);
if (isAV && isBV)
{
return(false); //parallel vertikal
}
if (isAH && isBH)
{
return(false); //parallel horizontal
}
if (isAH && isBV) //intersection h - v
{
result = new Point(segB.start.X, segA.start.Y);
return(isPointInSegment(segA, result) && isPointInSegment(segB, result));
}
if (isAV && isBH)
{
return(FindIntersectionPoint(segB, segA, out result)); //intersection v-h
}
if (isBV || isBH)
{
return(FindIntersectionPoint(segB, segA, out result)); //if only one is h or v make it segA
}
if (isAH) //only A is horizontal
{
result = new Point((int)getXAtY(segB, segA.start.Y), segA.start.Y);
return(isPointInSegment(segA, result) && isPointInSegment(segB, result));
}
if (isAV) //only A is vertical
{
result = new Point(segA.start.X, (int)getYAtX(segB, segA.start.X));
return(isPointInSegment(segA, result) && isPointInSegment(segB, result));
}
//both steep
//y = Ax + B
PointF fx1 = getFxForm(segA);
PointF fx2 = getFxForm(segB);
//Ax - y = -B
float A1 = fx1.X;
float B1 = -1;
float C1 = -fx1.Y;
float A2 = fx2.X;
float B2 = -1;
float C2 = -fx2.Y;
//Ax + By = C
float delta = A1 * B2 - A2 * B1;
if (delta == 0)
{
return(false);
}
result.X = (int)((B2 * C1 - B1 * C2) / delta);
result.Y = (int)((A1 * C2 - A2 * C1) / delta);
return(isPointInSegment(segA, result) && isPointInSegment(segB, result));
}
public static float getYAtX(LineSegment seg, int x)
{
PointF fx = getFxForm(seg);
return(fx.X * x + fx.Y);
}