public static Point?getIntersectionCoordinates(CustomLine l1, CustomLine l2)
{
Point intersectionPoint = new Point();
// if parallel
if (l1.getSlope() == l2.getSlope())
{
return(null);
}
// if either one is vertical (but not both because we would have returned null already)
else if (l1.getIsVertical())
{
intersectionPoint.X = l1.getPoint1().X;
Point l2Point = l2.getPoint1();
intersectionPoint.Y = (intersectionPoint.X * l2.getSlope()) + l2.getConstant();
}
else if (l2.getIsVertical())
{
intersectionPoint.X = l2.getPoint1().X;
Point l1Point = l1.getPoint1();
intersectionPoint.Y = (intersectionPoint.X * l1.getSlope()) + l1.getConstant();
}
else
{
Point l1Point = l1.getPoint1();
Point l2Point = l2.getPoint1();
double a1 = l1Point.Y - l1.getSlope() * l1Point.X;
double a2 = l2Point.Y - l2.getSlope() * l2Point.X;
intersectionPoint.X = (a1 - a2) / (l2.getSlope() - l1.getSlope());
intersectionPoint.Y = a2 + l2.getSlope() * intersectionPoint.X;
}
return(intersectionPoint);
}
public static Point ClosestPointFromPointToPolygon(CustomPolygon polygon, Point point)
{
// we keep track of point with minimum distance
Point? minPoint = null;
double minDist = double.MaxValue;
List <CustomLine> polygonLines = polygon.GetPolygonLines();
// for each line in polygon, find the perpendicular line from point
for (int i = 0; i < polygonLines.Count(); i++)
{
CustomLine lineSegment = polygonLines[i];
double slope = lineSegment.getSlope();
double perpSlope = CustomLine.getPerpendicularSlope(slope);
CustomLine perpLine = new CustomLine(point, perpSlope);
Point? intersectionPoint = CustomLine.getIntersectionCoordinates(lineSegment, perpLine);
if (intersectionPoint.HasValue)
{
double dist = Utilities.getDistance(intersectionPoint.Value, point);
// does this line intersect the polygon line segment?
// is the intersection point and the point a min distance
if (CustomLine.withinLineSegment(intersectionPoint.Value, lineSegment) &&
dist < minDist)
{
minDist = dist;
minPoint = intersectionPoint;
}
}
else
{
throw new Exception("Intersection Point is null even though it should have a coordinate");
}
}
// If there is a minpoint we are good to go
if (minPoint.HasValue)
{
return(minPoint.Value);
}
// or else we calculate the closest distance from the point to the polygon corners
else
{
minDist = double.MaxValue;
PointCollection points = polygon.GetPoints();
for (int i = 0; i < points.Count; i++)
{
double dist = Utilities.getDistance(points[i], point);
if (dist < minDist)
{
minDist = dist;
minPoint = points[i];
}
}
}
// If there is a minpoint we are good to go
if (minPoint.HasValue)
{
return(minPoint.Value);
}
else
{
throw new Exception("Point with minimum distance is null even though it should have a coordinate");
}
}
