public int GetClosestPoint (PointF p/*, out float dist*/)
{
var minIndex = -1;
var minDist = 0.0f;
for (var i = StartIndex; i <= EndIndex; i++) {
var d = _points [i].DistanceTo (p);
if (minIndex == -1 || (d < minDist)) {
minIndex = i;
minDist = d;
}
}
//dist = minDist;
return minIndex;
}