public SingleEyeGazeData SelectSingleEye(GazeData gaze)
{
var average = (gaze.LeftEye.Validity == EyeValidity.Valid && gaze.RightEye.Validity == EyeValidity.Valid)
? new EyeData(EyeValidity.Valid, EyeSampleUtils.Average(gaze.LeftEye, gaze.RightEye))
: EyeData.Default;
return(new SingleEyeGazeData(average, gaze.Timestamp));
}
// .-|.-|.-|
public static IObservable <EyeMovement> MergeAdjacentFixations(this IObservable <EyeMovement> movements, TimeSpan maxTimeBetweenFixations, double maxAngleBetweenFixations)
{
return(movements.Buffer(m => m.MovementType == EyeMovementType.Fixation)
.Scan((aggregate, buffer) =>
{
if (aggregate.Any())
{
var lastFixation = aggregate.FirstOrDefault(m => m.MovementType == EyeMovementType.Fixation);
var nextFixation = buffer.FirstOrDefault(m => m.MovementType == EyeMovementType.Fixation);
var nextMovements = buffer.Except(new[] { nextFixation }).ToArray();
if (lastFixation != null && nextFixation != null)
{
var timeBetweenFixations = (nextFixation.Timestamp - lastFixation.EndTimestamp);
if (timeBetweenFixations <= maxTimeBetweenFixations)
{
var lastSample = lastFixation.Samples.Last().Eye;
var nextSample = nextFixation.Samples.First().Eye;
var averageSample = EyeSampleUtils.Average(lastSample, nextSample);
double angle = averageSample.GetVisualAngle(lastFixation.AverageSample, nextFixation.AverageSample);
if (angle <= maxAngleBetweenFixations)
{
var mergedSamples = aggregate.SelectMany(m => m.Samples).Concat(nextFixation.Samples);
var newAverageSample = EyeSampleUtils.Average(lastFixation.Samples.Concat(nextFixation.Samples).Select(s => s.Eye));
// merge
var mergedFixation = new List <EyeMovement>()
{
new EyeMovement
(
EyeMovementType.Fixation,
mergedSamples,
newAverageSample,
lastFixation.Timestamp,
nextFixation.EndTimestamp
)
};
if (nextMovements != null && nextMovements.Any())
{
mergedFixation.AddRange(nextMovements);
}
return mergedFixation;
}
}
}
}
return buffer;
})
.Where(b => b.Any())
.Buffer((first, current) => first.First().Timestamp != current.First().Timestamp)
.Where(b => b.Any())
.Select(b => b.Last())
.SelectMany(b => b));
}
public static IObservable <EyeMovement> ClassifyMovements(this IObservable <EyeVelocity> velocities, double velocityThreshold)
{
return(velocities.Buffer((first, current) => ClassifyMovement(first, velocityThreshold) != ClassifyMovement(current, velocityThreshold))
.Where(b => b.Any())
.Buffer(2, 1)
.Scan <IList <IList <EyeVelocity> >, EyeMovement>(null, (movement, buffers) =>
{
var current = buffers.First();
var last = buffers.LastOrDefault();
var currentFirstSample = current.First();
DateTimeOffset startTimestamp = currentFirstSample.Eye.Timestamp;
if (movement != null)
{
var startTicksDiff = movement.EndTimestamp - movement.Samples.Last().Eye.Timestamp;
startTimestamp = startTimestamp.Subtract(startTicksDiff.Duration());
}
var currentLastSample = current.Last();
DateTimeOffset endTimestamp = currentLastSample.Eye.Timestamp;
if (last != null && last != current)
{
var endTicksDiff = (last.First().Eye.Timestamp - endTimestamp).Duration().Ticks / 2;
endTimestamp = endTimestamp.Add(TimeSpan.FromTicks(endTicksDiff));
}
EyeMovementType movementType = ClassifyMovement(current.First(), velocityThreshold);
EyeSample averageSample = null;
if (movementType == EyeMovementType.Fixation)
{
averageSample = EyeSampleUtils.Average(current.Select(s => s.Eye));
}
return new EyeMovement(movementType, current, averageSample, startTimestamp, endTimestamp);
}));
}