/// <summary>
/// Finds a point inside the polygon.
/// </summary>
public PointF GetInternalPoint()
{
int cvi = FindConvexVertex();
int prev = cvi > 0 ? cvi - 1 : _points.Count - 1;
int next = (cvi + 1) % _points.Count;
PointF v = _points[cvi];
PointF a = _points[prev];
PointF b = _points[next];
PointList pl = new PointList();
pl.Add(a); pl.Add(v); pl.Add(b);
Polygon avb = new Polygon(pl);
float minDist = float.MaxValue;
PointF intPt = v;
for (int i = 0; i < _points.Count; ++i)
{
if (i == cvi) continue;
if (i == prev) continue;
if (i == next) continue;
PointF q = _points[i];
if (avb.Contains(q))
{
float dist = (float)Math.Sqrt((q.X-v.X)*(q.X-v.X) + (q.Y-v.Y)*(q.Y-v.Y));
if (dist < minDist)
{
minDist = dist;
intPt = q;
}
}
}
if (intPt == v)
return new PointF((a.X + b.X) / 2, (a.Y + b.Y) / 2);
else
return new PointF((v.X + intPt.X)/ 2, (v.Y + intPt.Y) / 2);
}
/// <summary>
/// Creates single h-line at the specified vertical offset.
/// </summary>
private PointList BuildLine(float yOff)
{
PointF p11 = new PointF(_bounds.Left - 1, 0);
PointF p12 = new PointF(_bounds.Right + 1, 0);
PointF p21 = new PointF(_bounds.Left - 1, 0);
PointF p22 = new PointF(_bounds.Right + 1, 0);
p11.Y = p12.Y = yOff;
yOff += _text.Height;
if (yOff > _bounds.Bottom)
return null;
p21.Y = p22.Y = yOff;
ArrayList merge = new ArrayList();
PointList result = new PointList();
PointList row1 = PolygonIntersect(p11, p12);
PointList row2 = PolygonIntersect(p21, p22);
int i;
for (i = 0; i < row1.Count; i++)
merge.Add(new DirPt(row1[i], i % 2 == 1 ? 2 : 0));
for (i = 0; i < row2.Count; i++)
merge.Add(new DirPt(row2[i], i % 2 == 1 ? 3 : 1));
merge.Sort();
PointF pt = PointF.Empty;
int inter = -1; // 0 - for first line, 2 for second line, 4 - for both
for (i = 0; i < merge.Count; i++)
{
DirPt temp = merge[i] as DirPt;
if (temp.Direction == 2 || temp.Direction == 3) // out
{
if (inter != 4)
{
if (inter == 0 && temp.Direction == 2)
inter = -1;
else if (inter == 2 && temp.Direction == 3)
inter = -1;
continue;
}
pt.Y = yOff - _text.Height;
temp.Point = new PointF(temp.Point.X, yOff);
// Make points relative to the upper-left point of the polygon
pt.X -= _bounds.Left;
pt.Y -= _bounds.Top;
temp.Point = new PointF(
temp.Point.X - _bounds.Left,
temp.Point.Y - _bounds.Top);
result.Add(pt);
result.Add(temp.Point);
if (temp.Direction == 2)
inter = 2;
else
inter = 0;
}
else
{
pt = temp.Point;
if (temp.Direction == 0)
{
if (inter == -1)
inter = 0;
else if (inter == 2)
inter = 4;
}
else
{
if (inter == -1)
inter = 2;
else if (inter == 0)
inter = 4;
}
}
}
// Check if the center point of each
// rectangle lies within the polygon
for (i = 0; i < result.Count; )
{
PointF pt1 = result[i];
PointF pt2 = result[i + 1];
PointF ptc = PointF.Empty;
ptc.X = (pt1.X + pt2.X) / 2 + _bounds.Left;
ptc.Y = (pt1.Y + pt2.Y) / 2 + _bounds.Top;
if (!_polygon.Contains(ptc))
{
result.RemoveAt(i);
result.RemoveAt(i);
}
else
{
i += 2;
}
}
return result;
}
/// <summary>
/// Calculates the intersections between the
/// polygon and the line defined by the given points.
/// The result is a list containing all points of intersection.
/// </summary>
public PointList IntersectLine(PointF a, PointF b)
{
PointList result = new PointList();
PointF point;
for (int i = 0; i < _points.Count - 1; i++)
{
point = new Line(_points[i], _points[i + 1]).
IntersectLine(a, b);
if (!float.IsPositiveInfinity(point.X))
result.Add(point);
}
return result;
}