/// <summary>
/// The method looks for a stability region.
/// threshold value = limitValue + sigmaCoefficient * sigma;
/// </summary>
/// <param name="data">can't be null</param>
/// <param name="limitValue"></param>
/// <param name="sigmaCoefficient">defines filter amplitude and direction; see threshold value calculation</param>
/// <returns>
/// true cells defines stability region
/// false cells defines instability region
/// </returns>
public static bool[,] FindStabilityRegion(double[,] data, double sigmaFactor, BinaryFunction predicate, double limitValue = 1)
{
int rows = data.GetLength(0);
int columns = data.GetLength(1);
List <double> deviations = new List <double>();
for (int row = 0; row < rows; ++row)
{
for (int column = 0; column < columns; ++column)
{
double value = data[row, column];
if (row - 1 >= 0)
{
double delta = data[row - 1, column] - value;
deviations.Add(delta);
}
if (row < rows - 1)
{
double delta = data[row + 1, column] - value;
deviations.Add(delta);
}
if (column - 1 >= 0)
{
double delta = data[row, column - 1] - value;
deviations.Add(delta);
}
if (column < columns - 1)
{
double delta = data[row, column + 1] - value;
deviations.Add(delta);
}
}
}
double sigma = Statistics.CalculateSampleVariance(deviations.ToArray());
sigma = NumericalMethods.Sqrt(sigma);
sigma *= sigmaFactor;
double threshold = predicate(1, 0) ? (limitValue - sigma) : (limitValue + sigma);
bool[,] result = new bool[rows, columns];
for (int row = 0; row < rows; ++row)
{
for (int column = 0; column < columns; ++column)
{
result[row, column] = predicate(data[row, column], threshold);
}
}
double ry = NumericalMethods.Sqrt(rows);
double rx = NumericalMethods.Sqrt(columns);
int r = (int)Math.Min(rx, ry) - 1;
for (int index = 0; index < r; ++index)
{
result = Morphology.Erosion(result);
}
return(result);
}
public static List <Pixel2> FindStabilityExtremums(double[,] data, double sigmaFactor, BinaryFunction predicate)
{
List <Pixel2> result = new List <Pixel2>();
bool[,] region = FindStabilityRegion(data, sigmaFactor, predicate);
for (; ;)
{
int row = -1;
int column = -1;
bool status = NumericalMethods.FindConditionalExtremum(data, region, predicate, out row, out column);
if (!status)
{
break;
}
result.Add(new Pixel2(column, row));
region = Morphology.Erosion(region, row, column);
}
return(result);
}
