public static double MeanIfPixel(this MatrixData input, Func <double, bool> condition)
{
List <double> colMean = new List <double>();
for (int c = 0; c < input.NumberOfColumns; c++)
{
double d = input.MeanIf(c, condition);
if (condition(d))
{
colMean.Add(d);
}
}
return(colMean.Average());
}