public static double EndDirection(this Stroke stroke, int diffIdx)
{
PointSection sect = new PointSection(stroke[Math.Max(0, stroke.Count - 1 - diffIdx)].Pos,
stroke[stroke.Count - 1].Pos);
return(sect.Direction());
}
public static double Direction(this PointSection section)
{
double dx = (double)(section.End.X - section.Start.X);
double dy = (double)(section.End.Y - section.Start.Y);
return(Math.Atan2(dy, dx));
}
public static double StartDirection(this Stroke stroke, int diffIdx)
{
PointSection sect = new PointSection(stroke.Start.Pos, stroke[Math.Min(stroke.Count - 1, diffIdx)].Pos);
return(sect.Direction());
}