public static double Compute(double[] X, GaussianMixtureModel GMM)
{
// Initialisations
int K = GMM.K;
double[,] membership = new double[GMM.K, X.Length];
int count = 0;
double?logLikelihood = null;
while (count++ < 100)
{
// Expectation - recalculate membership values for all k,x pairs
int XLength = X.Length;
for (int x = 0; x < XLength; x++)
{
double total = 0.0;
for (int k = 0; k < K; k++)
{
membership[k, x] = GMM.MixingWeight[k] * GMM.SingleGaussianProbabilityEM(X[x], k);
total += membership[k, x];
}
for (int k = 0; k < K; k++)
{
membership[k, x] /= total;
}
}
// Maximisation - recalculate GMM parameters based on the results of the expectation step
for (int k = 0; k < K; k++)
{
// Mean
double sumMembership = 0.0;
double sumMembershipX = 0.0;
for (int x = 0; x < XLength; x++)
{
sumMembership += membership[k, x];
sumMembershipX += membership[k, x] * X[x];
}
GMM.Mean[k] = sumMembershipX / sumMembership;
// Sigma
double Mean = GMM.Mean[k];
double sumMembershipXMinusMeanSquared = 0.0;
for (int x = 0; x < XLength; x++)
{
sumMembershipXMinusMeanSquared += membership[k, x] * Math.Pow(X[x] - Mean, 2.0);
}
// Prevent Sigma from going below 1 to avoid S.Ds of 0
GMM.Sigma[k] = Math.Max(Math.Sqrt(sumMembershipXMinusMeanSquared / sumMembership), 1);
// Mixing
GMM.MixingWeight[k] = sumMembership / XLength;
}
// Log likelihood
double currentLikelihood = 1.0;
for (int x = 0; x < XLength; x++)
{
double value = X[x];
double total = 0.0;
for (int k = 0; k < K; k++)
{
total += GMM.MixingWeight[k] * GMM.SingleGaussianProbabilityEM(value, k);
}
currentLikelihood += Math.Log(total);
}
if (logLikelihood == null)
{
logLikelihood = currentLikelihood;
}
else
{
double ratio = currentLikelihood / (double)logLikelihood;
logLikelihood = currentLikelihood;
if (1 - ratio < 0.0001)
{
// Convergence
break;
}
}
}
return(logLikelihood == null ? Double.NaN : (double)logLikelihood);
}
protected override void OnDoWork(DoWorkEventArgs e)
{
List <Tuple <EMPatch, GaussianMixtureModel> > currentMixtures = new List <Tuple <EMPatch, GaussianMixtureModel> >();
int patchProgressCount = 0;
int totalPatches = Patches.Count;
foreach (EMPatch patch in Patches)
{
// Check bounds
if (patch.Left < 0 || patch.Right > Width || patch.Top < 0 || patch.Bottom > Height)
{
throw new EMPatch.EMPatchException("Patch falls outside the bounds of the source image");
}
// Copy data
int patchWidth = patch.Right - patch.Left;
int patchHeight = patch.Bottom - patch.Top;
int left = patch.Left, right = patch.Right, top = patch.Top, bottom = patch.Bottom;
if (this.data == null || this.data.Length != patchWidth * patchHeight)
{
this.data = new double[patchWidth * patchHeight];
}
int i = 0;
double max = Double.MinValue, min = Double.MaxValue;
for (int pX = left; pX < right; pX++)
{
for (int pY = top; pY < bottom; pY++)
{
data[i] = IntensityBuffer[pY * Width + pX];
if (data[i] < min)
{
min = data[i];
}
if (data[i] > max)
{
max = data[i];
}
i += 1;
}
}
GaussianMixtureModel GMM = null;
// Run EM starting at the initial class count and increasing the class count if necessary
for (int classCount = Configuration.InitialClassCount; classCount <= Configuration.MaximumClassCount; classCount++)
{
// KMeans initialisation
GMM = GaussianMixtureModel.KMeansInitialisation(data, classCount, (int)min, (int)max);
// Expectation Maximisation
ExpectationMaximisation.Compute(data, GMM);
// Threshold
GMM.ThresholdAtPercentage(Configuration.BackgroundPercentage, Configuration.BackgroundExcessSigma);
// Check remaining classes for none (empty patch) or the correct number of classes
if (GMM.K - (GMM.ThresholdK + 1) >= Configuration.ExpectedRootClassCount ||
GMM.K - (GMM.ThresholdK + 1) == 0)
{
break;
}
}
// Add Patch, GMM pair into output array
if (GMM == null)
{
throw new InvalidOperationException("GMM cannot be null");
}
currentMixtures.Add(new Tuple <EMPatch, GaussianMixtureModel>(patch, GMM));
// Signal progress changed
base.OnProgressChanged(new ProgressChangedEventArgs((int)(++patchProgressCount * 100.0 / totalPatches), null));
}
// Assign this.Mixtures
this.Mixtures = currentMixtures;
}