/// <summary>
/// Finds valeys and peaks.
/// </summary>
/// <param name="contourPts">Contour.</param>
/// <param name="selector">Filter function where peak or valey is choosen. Angle range can be determined also. </param>
/// <param name="scale">A good value is ~15. A specified amount will be skipped every time to avoid local minima.</param>
/// <param name="peaks">Found peaks.</param>
/// <param name="valeys">Found valeys.</param>
/// <remarks>
/// Sample usage:
/// <code>
/// contourPts.FindExtremaIndices((angle, isPeak)=>
/// {
/// if ((isPeak AND angle ;gt 0 AND angle ;lt 90) || //peak filtering
/// (!isPeak AND angle ;gt 0 AND angle ;lt 90)) //valey filtering
/// return true;
///
/// return false;
/// },
/// scale, out peakIndeces, out valeyIndeces);
/// </code>
/// </remarks>
public static void FindExtremaIndices(this IList<Point> contourPts, Func<float, bool, bool> selector, int scale,
out List<int> peaks, out List<int> valeys)
{
peaks = new List<int>(); valeys = new List<int>();
for (int i = 0; i < contourPts.Count; i++)
{
var idxL = (i - scale) % contourPts.Count; if (idxL < 0) idxL = contourPts.Count + idxL;
var idxC = i;
var idxR = (i + scale) % contourPts.Count;
Vector2D v1 = new Vector2D(contourPts[idxC], contourPts[idxL]);
Vector2D v2 = new Vector2D(contourPts[idxC], contourPts[idxR]);
var angle = System.Math.Acos(Vector2D.DotProduct(v1, v2)) * 180 / System.Math.PI;
var z = Vector2D.CrossProduct(v1, v2);
bool isPeak = z >= 0;
if (selector((float)angle, isPeak))
{
if (isPeak)
{
peaks.Add(i);
}
else
{
valeys.Add(i);
}
}
}
}
private static LineSegment2DF getLine(int derivativeOrientation, PointF centerPoint, float length)
{
Vector2D vec = new Vector2D(Angle.ToRadians(derivativeOrientation)).Multiply(length / 2);
var p1 = vec.Add(centerPoint);
var p2 = vec.Negate().Add(centerPoint);
return new LineSegment2DF(p1.ToPoint(), p2.ToPoint());
}
/// <summary>
/// Multiplies vector and scale.
/// </summary>
/// <param name="vector"><see cref="Vector2D"/>.</param>
/// <param name="scale">Scale</param>
/// <returns>New scaled <see cref="Vector2D"/>.</returns>
public static Vector2D Multiply(Vector2D vector, float scale)
{
return new Vector2D(vector.X * scale, vector.Y * scale);
}
/// <summary>
/// Normalizes the vector with its length and produces a new vector.
/// </summary>
/// <returns>Normalized vector.</returns>
public Vector2D Normalize()
{
var norm = (float)this.Length;
var v = new Vector2D(this.X / norm, this.Y / norm);
return v;
}
/// <summary>
/// Adds point and <see cref="Vector2D"/>.
/// </summary>
/// <param name="point">Point.</param>
/// <param name="vector">Vector.</param>
/// <returns> Translated point. </returns>
public static PointF Add(PointF point, Vector2D vector)
{
return new PointF
{
X = point.X + vector.X,
Y = point.Y + vector.Y
};
}
/// <summary>
/// Gets whether two vectors have opposite directions or not.
/// </summary>
/// <param name="v1">First vector</param>
/// <param name="v2">Second vector</param>
/// <returns>True if two vectors have opposite directions, otherwise false.</returns>
public static bool AreOpositeDirection(Vector2D v1, Vector2D v2)
{
return v1.X == -v2.X && v1.Y == -v2.Y;
}
/// <summary>
/// Vector obtained by cross product in 2D is facing toward Z direction (other coordinates are zero)
/// </summary>
/// <param name="v1">First vector</param>
/// <param name="v2">Second vector</param>
/// <returns>Vector signed magnitude in Z direction.</returns>
public static double CrossProduct(Vector2D v1, Vector2D v2)
{
return (v1.X * v2.Y) - (v1.Y * v2.X);
}
/// <summary>
/// Calculates vectors dot product.
/// </summary>
/// <param name="v1">First vector.</param>
/// <param name="v2">Second vector.</param>
/// <returns>Dot product magnitude.</returns>
public static double DotProduct(Vector2D v1, Vector2D v2)
{
double dotProduct = v1.X * v2.X + v1.Y * v2.Y;
dotProduct /= v1.Length;
dotProduct /= v2.Length;
dotProduct = System.Math.Min(dotProduct, 1);
return dotProduct;
}
/// <summary>
/// Calculates angle between vectors (in radians).
/// <seealso cref="Angle"/>
/// </summary>
/// <param name="v1">First vector.</param>
/// <param name="v2">Second vector.</param>
/// <returns>Angle between vectors in radians.</returns>
public static double Angle(Vector2D v1, Vector2D v2)
{
double cosAngle = DotProduct(v1, v2);
double angleRad = System.Math.Acos(cosAngle);
return angleRad;
}
