public static IPolygon Offset(this IPolygon p, double offset)
{
if (p.IsEmpty)
{
return(Polygon.Empty);
}
var boundingBox = p.BoundingBox().Offset(Math.Max(offset, 0));
double scale = Math.Max(boundingBox.Width, boundingBox.Height);
var fixedPointRange = new Box2(boundingBox.MinCorner, new Vector2(scale, scale));
var fixedP = ConvertToFixedPoint(p, fixedPointRange);
try
{
var offsetter = new ClipperOffset();
offsetter.AddPaths(fixedP, JoinType.jtMiter, EndType.etClosedPolygon);
var fixedAnswer = new ClipperPolygon();
offsetter.Execute(ref fixedAnswer, offset * _fixedPointRange / scale);
return(ConvertToFloatingPoint(fixedAnswer, fixedPointRange));
}
catch (Exception e)
{
Console.WriteLine("EXCEPTION: {0}", e);
return(p);
}
}
private static IPolygon BinaryOperation(IPolygon p, IPolygon q, ClipType operationType)
{
if (p.IsEmpty && q.IsEmpty)
{
return(Polygon.Empty);
}
var boundingBox = Box2.Hull(p.BoundingBox(), q.BoundingBox());
var fixedP = ConvertToFixedPoint(p, boundingBox);
var fixedQ = ConvertToFixedPoint(q, boundingBox);
try
{
var clipper = new Clipper();
clipper.AddPaths(fixedP, PolyType.ptSubject, closed: true);
clipper.AddPaths(fixedQ, PolyType.ptClip, closed: true);
var fixedAnswer = new ClipperPolygon();
clipper.Execute(operationType, fixedAnswer);
return(ConvertToFloatingPoint(fixedAnswer, boundingBox));
}
catch (Exception e)
{
Console.WriteLine("EXCEPTION: {0}", e);
return(Polygon.Empty);
}
}
// intersection of polygon with half plane lying on negative (left) side of line: this is the natural convention since we use external normals
public static IPolygon CropBy(this IPolygon p, Line2 line)
{
var box = p.BoundingBox();
var point = line.Project(box.Center);
var radius = box.Diameter / 2;
var collinearDisplacement = radius * line.Direction;
var transverseDisplacement = 2 * collinearDisplacement.Rotate90();
var vertex1 = point + collinearDisplacement;
var vertex2 = point - collinearDisplacement;
var vertices = new List <Vector2>
{
vertex1,
vertex1 + transverseDisplacement,
vertex2 + transverseDisplacement,
vertex2
};
var square = new Polygon(vertices);
return(Intersection(p, square));
}
public static IPolygon Opening(this IPolygon p, double offset)
{
if (offset < 0)
{
throw new ArgumentOutOfRangeException("offset", offset, "Expected positive offset");
}
return(Clopening(p, p.BoundingBox(), -offset));
}
public static IPolygon Closing(this IPolygon p, double offset)
{
if (offset < 0)
{
throw new ArgumentOutOfRangeException("offset", offset, "Expected positive offset");
}
var boundingBox = p.BoundingBox().Offset(offset);
return(Clopening(p, boundingBox, offset));
}
public static IPolygon RelativeClosing(this IPolygon p, double relativeOffset)
{
if (relativeOffset < 0)
{
throw new ArgumentOutOfRangeException("relativeOffset", relativeOffset, "Expected positive relativeOffset");
}
var boundingBox = p.BoundingBox();
if (boundingBox.IsEmpty)
{
return(Polygon.Empty);
}
double scale = Math.Max(boundingBox.Width, boundingBox.Height);
return(p.Closing(relativeOffset * scale));
}
public static IPolygon MinkowskiDifference(IPolygon p, IPolygon q)
{
if (p.IsEmpty || q.IsEmpty)
{
return(Polygon.Empty);
}
var boundingBox = Box2.Hull(p.BoundingBox(), q.BoundingBox());
boundingBox = Box2.Hull(boundingBox, new Box2(-boundingBox.MaxCorner, boundingBox.Dimensions));
var fixedAnswer = new ClipperPolygon();
var fixedP = ConvertToFixedPoint(p, boundingBox);
foreach (var qContour in q.Contours)
{
var fixedQContour = MinusConvertToFixedPoint(qContour, boundingBox);
try
{
var clipper = new Clipper();
clipper.AddPaths(fixedAnswer, PolyType.ptSubject, closed: true);
clipper.AddPaths(Clipper.MinkowskiSum(fixedQContour, fixedP, pathIsClosed: true), PolyType.ptClip, closed: true);
var tempAnswer = new ClipperPolygon();
clipper.Execute(ClipType.ctUnion, tempAnswer);
fixedAnswer = tempAnswer;
}
catch (Exception e)
{
Console.WriteLine("EXCEPTION: {0}", e);
}
}
return(ConvertToFloatingPoint(fixedAnswer, boundingBox));
}
