/// <summary>
/// Changes the envelope extent by the specified amount relative
/// to it's current extent in that dimension (preserving the aspect ratio).
/// So Zoom(10) on a 100 unit wide envelope creates a 110 unit wide envlope,
/// while Zoom(-10) on a 100 unit wide envelope creates a 90 unit wide envelope.
/// Zoom(-100) on an envelope makes it 100% smaller, or effectively a point.
/// Tragically, a point cannot be "zoomed" back in, so a check should be used
/// to ensure that the envelope is not currently a point before attempting
/// to zoom in.
/// </summary>
/// <param name="self">The IEnvelope that this zoom method modifies</param>
/// <param name="percent">
/// Positive 50 makes the envelope 50% larger
/// Negative 50 makes the envelope 50% smaller
/// </param>
/// <example>
/// perCent = -50 compact the envelope a 50% (make it smaller).
/// perCent = 200 enlarge envelope by 2.
/// </example>
public static void Zoom(this IEnvelope self, double percent)
{
if (self == null)
{
return;
}
if (self.IsNull)
{
return;
}
double ratio = percent / 100;
Coordinate size = new Coordinate();
for (int i = 0; i < self.NumOrdinates; i++)
{
double oldSize = self.Maximum[i] - self.Minimum[i];
size[i] = oldSize + ratio * oldSize;
}
SetCenter(self, self.Center(), size);
}
/// <summary>
/// The original algorithm simply allows edges that have one defined point and
/// another "NAN" point. Simply excluding the not a number coordinates fails
/// to preserve the known direction of the ray. We only need to extend this
/// long enough to encounter the bounding box, not infinity.
/// </summary>
/// <param name="graph">The VoronoiGraph with the edge list.</param>
/// <param name="bounds">The polygon bounding the datapoints.</param>
private static void HandleBoundaries(VoronoiGraph graph, IEnvelope bounds)
{
List <ILineString> boundSegments = new List <ILineString>();
List <VoronoiEdge> unboundEdges = new List <VoronoiEdge>();
// Identify bound edges for intersection testing
foreach (VoronoiEdge edge in graph.Edges)
{
if (edge.VVertexA.ContainsNan() || edge.VVertexB.ContainsNan())
{
unboundEdges.Add(edge);
continue;
}
boundSegments.Add(
new LineString(new List <Coordinate> {
edge.VVertexA.ToCoordinate(), edge.VVertexB.ToCoordinate()
}));
}
// calculate a length to extend a ray to look for intersections
IEnvelope env = bounds;
double h = env.Height;
double w = env.Width;
double len = Math.Sqrt((w * w) + (h * h));
// len is now long enough to pass entirely through the dataset no matter where it starts
foreach (VoronoiEdge edge in unboundEdges)
{
// the unbound line passes thorugh start
Coordinate start = (edge.VVertexB.ContainsNan())
? edge.VVertexA.ToCoordinate()
: edge.VVertexB.ToCoordinate();
// the unbound line should have a direction normal to the line joining the left and right source points
double dx = edge.LeftData.X - edge.RightData.X;
double dy = edge.LeftData.Y - edge.RightData.Y;
double l = Math.Sqrt((dx * dx) + (dy * dy));
// the slope of the bisector between left and right
double sx = -dy / l;
double sy = dx / l;
Coordinate center = bounds.Center();
if ((start.X > center.X && start.Y > center.Y) || (start.X < center.X && start.Y < center.Y))
{
sx = dy / l;
sy = -dx / l;
}
Coordinate end1 = new Coordinate(start.X + (len * sx), start.Y + (len * sy));
Coordinate end2 = new Coordinate(start.X - (sx * len), start.Y - (sy * len));
Coordinate end = (end1.Distance(center) < end2.Distance(center)) ? end2 : end1;
if (bounds.Contains(end))
{
end = new Coordinate(start.X - (sx * len), start.Y - (sy * len));
}
if (edge.VVertexA.ContainsNan())
{
edge.VVertexA = new Vector2(end.ToArray());
}
else
{
edge.VVertexB = new Vector2(end.ToArray());
}
}
}
/// <summary>
/// The original algorithm simply allows edges that have one defined point and
/// another "NAN" point. Simply excluding the not a number coordinates fails
/// to preserve the known direction of the ray. We only need to extend this
/// long enough to encounter the bounding box, not infinity.
/// </summary>
/// <param name="graph">The VoronoiGraph with the edge list</param>
/// <param name="bounds">The polygon bounding the datapoints</param>
private static void HandleBoundaries(VoronoiGraph graph, IEnvelope bounds)
{
List<ILineString> boundSegments = new List<ILineString>();
List<VoronoiEdge> unboundEdges = new List<VoronoiEdge>();
// Identify bound edges for intersection testing
foreach (VoronoiEdge edge in graph.Edges)
{
if(edge.VVertexA.ContainsNan() || edge.VVertexB.ContainsNan())
{
unboundEdges.Add(edge);
continue;
}
boundSegments.Add(new LineString(new List<Coordinate>{edge.VVertexA.ToCoordinate(), edge.VVertexB.ToCoordinate()}));
}
// calculate a length to extend a ray to look for intersections
IEnvelope env = bounds;
double h = env.Height;
double w = env.Width;
double len = Math.Sqrt(w * w + h * h); // len is now long enough to pass entirely through the dataset no matter where it starts
foreach (VoronoiEdge edge in unboundEdges)
{
// the unbound line passes thorugh start
Coordinate start = (edge.VVertexB.ContainsNan())
? edge.VVertexA.ToCoordinate()
: edge.VVertexB.ToCoordinate();
// the unbound line should have a direction normal to the line joining the left and right source points
double dx = edge.LeftData.X - edge.RightData.X;
double dy = edge.LeftData.Y - edge.RightData.Y;
double l = Math.Sqrt(dx*dx + dy*dy);
// the slope of the bisector between left and right
double sx = -dy/l;
double sy = dx/l;
Coordinate center = bounds.Center();
if((start.X > center.X && start.Y > center.Y) || (start.X < center.X && start.Y < center.Y))
{
sx = dy/l;
sy = -dx/l;
}
Coordinate end1 = new Coordinate(start.X + len*sx, start.Y + len * sy);
Coordinate end2 = new Coordinate(start.X - sx * len, start.Y - sy * len);
Coordinate end = (end1.Distance(center) < end2.Distance(center)) ? end2 : end1;
if(bounds.Contains(end))
{
end = new Coordinate(start.X - sx * len, start.Y - sy * len);
}
if (edge.VVertexA.ContainsNan())
{
edge.VVertexA = new Vector2(end.ToArray());
}
else
{
edge.VVertexB = new Vector2(end.ToArray());
}
}
}
