// use the clipper library to return an offset to the given polygon. Positive offset expands the polygon, negative contracts
// note that this returns an array of polygons
public static NFP[] polygonOffsetDeepNest(NFP polygon, double offset, double clipperScale, double curveTolerance = 0.72)
{
if (offset == 0 || GeometryUtil._almostEqual(offset, 0))
{
return(new[] { polygon });
}
var p = svgToClipper(polygon, clipperScale).ToList();
var miterLimit = 4;
var co = new ClipperLib.ClipperOffset(miterLimit, curveTolerance * clipperScale);
co.AddPath(p.ToList(), ClipperLib.JoinType.jtMiter, ClipperLib.EndType.etClosedPolygon);
var newpaths = new List <List <ClipperLib.IntPoint> >();
co.Execute(ref newpaths, offset * clipperScale);
var result = new List <NFP>();
for (var i = 0; i < newpaths.Count; i++)
{
result.Add(clipperToSvg(newpaths[i], clipperScale));
}
return(result.ToArray());
}
public static NFP cleanPolygon2(NFP polygon, double clipperScale, double curveTolerance = 0.72)
{
var p = svgToClipper(polygon, clipperScale);
// remove self-intersections and find the biggest polygon that's left
var simple = ClipperLib.Clipper.SimplifyPolygon(p.ToList(), ClipperLib.PolyFillType.pftNonZero);
if (simple == null || simple.Count == 0)
{
return(null);
}
var biggest = simple[0];
var biggestarea = Math.Abs(ClipperLib.Clipper.Area(biggest));
for (var i = 1; i < simple.Count; i++)
{
var area = Math.Abs(ClipperLib.Clipper.Area(simple[i]));
if (area > biggestarea)
{
biggest = simple[i];
biggestarea = area;
}
}
// clean up singularities, coincident points and edges
var clean = ClipperLib.Clipper.CleanPolygon(biggest, 0.01 *
curveTolerance * clipperScale);
if (clean == null || clean.Count == 0)
{
return(null);
}
var cleaned = clipperToSvg(clean, clipperScale);
// remove duplicate endpoints
var start = cleaned[0];
var end = cleaned[cleaned.Length - 1];
if (start == end || (GeometryUtil._almostEqual(start.X, end.X) &&
GeometryUtil._almostEqual(start.Y, end.Y)))
{
cleaned.Points = cleaned.Points.Take(cleaned.Points.Count() - 1).ToArray();
}
return(cleaned);
}
public static NFP simplifyFunction(NFP polygon, bool inside, double clipperScale, double curveTolerance = 0.72, bool hullSimplify = false)
{
var tolerance = 4 * curveTolerance;
// give special treatment to line segments above this length (squared)
var fixedTolerance = 40 * curveTolerance * 40 * curveTolerance;
int i, j, k;
if (hullSimplify)
{
// use convex hull
var hull = getHull(polygon);
if (hull != null)
{
return(hull);
}
else
{
return(polygon);
}
}
var cleaned = cleanPolygon2(polygon, clipperScale);
if (cleaned != null && cleaned.Length > 1)
{
polygon = cleaned;
}
else
{
return(polygon);
}
// polygon to polyline
var copy = polygon.slice(0);
copy.push(copy[0]);
// mark all segments greater than ~0.25 in to be kept
// the PD simplification algo doesn't care about the accuracy of long lines, only the absolute distance of each point
// we care a great deal
for (i = 0; i < copy.Length - 1; i++)
{
var p1 = copy[i];
var p2 = copy[i + 1];
var sqd = (p2.X - p1.X) * (p2.X - p1.X) + (p2.Y - p1.Y) * (p2.Y - p1.Y);
if (sqd > fixedTolerance)
{
p1.marked = true;
p2.marked = true;
}
}
var simple = Simplify.simplify(copy, tolerance, true);
// now a polygon again
//simple.pop();
simple.Points = simple.Points.Take(simple.Points.Count() - 1).ToArray();
// could be dirty again (self intersections and/or coincident points)
simple = cleanPolygon2(simple, clipperScale);
// simplification process reduced poly to a line or point
if (simple == null)
{
simple = polygon;
}
var offsets = polygonOffsetDeepNest(simple, inside ? -tolerance : tolerance, clipperScale);
NFP offset = null;
double offsetArea = 0;
List <NFP> holes = new List <NFP>();
for (i = 0; i < offsets.Length; i++)
{
var area = GeometryUtil.polygonArea(offsets[i]);
if (offset == null || area < offsetArea)
{
offset = offsets[i];
offsetArea = area;
}
if (area > 0)
{
holes.Add(offsets[i]);
}
}
// mark any points that are exact
for (i = 0; i < simple.Length; i++)
{
var seg = new NFP();
seg.AddPoint(simple[i]);
seg.AddPoint(simple[i + 1 == simple.Length ? 0 : i + 1]);
var index1 = find(seg[0], polygon);
var index2 = find(seg[1], polygon);
if (index1 + 1 == index2 || index2 + 1 == index1 || (index1 == 0 && index2 == polygon.Length - 1) || (index2 == 0 && index1 == polygon.Length - 1))
{
seg[0].exact = true;
seg[1].exact = true;
}
}
var numshells = 4;
NFP[] shells = new NFP[numshells];
for (j = 1; j < numshells; j++)
{
var delta = j * (tolerance / numshells);
delta = inside ? -delta : delta;
var shell = polygonOffsetDeepNest(simple, delta, clipperScale);
if (shell.Count() > 0)
{
shells[j] = shell.First();
}
else
{
//shells[j] = shell;
}
}
if (offset == null)
{
return(polygon);
}
// selective reversal of offset
for (i = 0; i < offset.Length; i++)
{
var o = offset[i];
var target = getTarget(o, simple, 2 * tolerance);
// reverse point offset and try to find exterior points
var test = clone(offset);
test.Points[i] = new SvgPoint(target.X, target.Y);
if (!exterior(test, polygon, inside))
{
o.X = target.X;
o.Y = target.Y;
}
else
{
// a shell is an intermediate offset between simple and offset
for (j = 1; j < numshells; j++)
{
if (shells[j] != null)
{
var shell = shells[j];
var delta = j * (tolerance / numshells);
target = getTarget(o, shell, 2 * delta);
test = clone(offset);
test.Points[i] = new SvgPoint(target.X, target.Y);
if (!exterior(test, polygon, inside))
{
o.X = target.X;
o.Y = target.Y;
break;
}
}
}
}
}
// straighten long lines
// a rounded rectangle would still have issues at this point, as the long sides won't line up straight
var straightened = false;
for (i = 0; i < offset.Length; i++)
{
var p1 = offset[i];
var p2 = offset[i + 1 == offset.Length ? 0 : i + 1];
var sqd = (p2.X - p1.X) * (p2.X - p1.X) + (p2.Y - p1.Y) * (p2.Y - p1.Y);
if (sqd < fixedTolerance)
{
continue;
}
for (j = 0; j < simple.Length; j++)
{
var s1 = simple[j];
var s2 = simple[j + 1 == simple.Length ? 0 : j + 1];
var sqds = (p2.X - p1.X) * (p2.X - p1.X) + (p2.Y - p1.Y) * (p2.Y - p1.Y);
if (sqds < fixedTolerance)
{
continue;
}
if ((GeometryUtil._almostEqual(s1.X, s2.X) || GeometryUtil._almostEqual(s1.Y, s2.Y)) && // we only really care about vertical and horizontal lines
GeometryUtil._withinDistance(p1, s1, 2 * tolerance) &&
GeometryUtil._withinDistance(p2, s2, 2 * tolerance) &&
(!GeometryUtil._withinDistance(p1, s1, curveTolerance / 1000) ||
!GeometryUtil._withinDistance(p2, s2, curveTolerance / 1000)))
{
p1.X = s1.X;
p1.Y = s1.Y;
p2.X = s2.X;
p2.Y = s2.Y;
straightened = true;
}
}
}
//if(straightened){
var Ac = ClipperHelper.ScaleUpPaths(offset, 10000000);
var Bc = ClipperHelper.ScaleUpPaths(polygon, 10000000);
var combined = new List <List <IntPoint> >();
var clipper = new ClipperLib.Clipper();
clipper.AddPath(Ac.ToList(), ClipperLib.PolyType.ptSubject, true);
clipper.AddPath(Bc.ToList(), ClipperLib.PolyType.ptSubject, true);
// the line straightening may have made the offset smaller than the simplified
if (clipper.Execute(ClipperLib.ClipType.ctUnion, combined, ClipperLib.PolyFillType.pftNonZero, ClipperLib.PolyFillType.pftNonZero))
{
double?largestArea = null;
for (i = 0; i < combined.Count; i++)
{
var n = toNestCoordinates(combined[i].ToArray(), 10000000);
var sarea = -GeometryUtil.polygonArea(n);
if (largestArea == null || largestArea < sarea)
{
offset = n;
largestArea = sarea;
}
}
}
//}
cleaned = cleanPolygon2(offset, clipperScale);
if (cleaned != null && cleaned.Length > 1)
{
offset = cleaned;
}
// mark any points that are exact (for line merge detection)
for (i = 0; i < offset.Length; i++)
{
var seg = new SvgPoint[] { offset[i], offset[i + 1 == offset.Length ? 0 : i + 1] };
var index1 = find(seg[0], polygon);
var index2 = find(seg[1], polygon);
if (index1 == null)
{
index1 = 0;
}
if (index2 == null)
{
index2 = 0;
}
if (index1 + 1 == index2 || index2 + 1 == index1 ||
(index1 == 0 && index2 == polygon.Length - 1) ||
(index2 == 0 && index1 == polygon.Length - 1))
{
seg[0].exact = true;
seg[1].exact = true;
}
}
if (!inside && holes != null && holes.Count > 0)
{
offset.Childrens = holes;
}
return(offset);
}
