public List <Saccade> GenerateSaccades(List <Fixation> fixations)
{
List <Saccade> saccades = new List <Saccade>();
for (int i = 0; i < fixations.Count - 1; i++)
{
Fixation from = fixations[i];
Fixation to = fixations[i + 1];
Saccade s = new Saccade(new Point(from.x, from.y), new Point(to.x, to.y));
saccades.Add(s);
}
return(saccades);
}
// Converts raw gaze input into fixations.
public List <Fixation> CalculateFixations(int windowSize, float peakThreshold, float radius, int clipAmount)
{
ClipRawPoints(clipAmount);
if (rawPoints == null || rawPoints.Count == 0)
{
Console.WriteLine("RawPoints is null or contains no points. Unable to calculate fixations.");
return(new List <Fixation>());
}
Console.WriteLine("Calculating fixations...");
List <Point> allPoints = ConvertGazePointsToPoints(rawPoints);
// Create the array to store the differences in the windows for each point.
float[] differences = new float[rawPoints.Count];
for (int i = 0; i < rawPoints.Count; i++)
{
differences[i] = 0;
}
// 1: find the mean of the sliding window before and after sample i
for (int i = windowSize; i <= (rawPoints.Count - windowSize) - 1; i++)
{
List <Point> leftWindow = allPoints.GetRange(i - windowSize, windowSize);
List <Point> rightWindow = allPoints.GetRange(i + 1, windowSize);
Point meanBefore = GeometricMean(leftWindow);
Point meanAfter = GeometricMean(rightWindow);
// 2: create vector "d", with distances between before and after windows
float axbxSquared = (meanBefore.x - meanAfter.x) * (meanBefore.x - meanAfter.x);
float aybySquared = (meanBefore.y - meanAfter.y) * (meanBefore.y - meanAfter.y);
float difference = (float)Math.Sqrt(axbxSquared + aybySquared);
differences[i] = difference;
}
// Testing
/*
* Console.WriteLine("Differences:");
* int count = 0;
* foreach(float difference in differences) {
* Console.Write(count++ + ":" + difference + ", ");
* }
* Console.Write("\n");
*/
// End Testing
// 3: create peak vector and find peaks (that is, find the large(est) differences in means of the sliding windows)
// Create the array to store the differences in the windows for each point.
float[] peaks = new float[rawPoints.Count];
for (int i = 0; i < rawPoints.Count; i++)
{
peaks[i] = 0;
}
for (int i = 1; i < rawPoints.Count - 1; i++)
{
// if this is a peak
if (differences[i] > differences[i - 1] && differences[i] > differences[i + 1])
{
peaks[i] = differences[i];
}
}
// Testing
/*
* Console.WriteLine("Peaks:");
* count = 0;
* foreach(float peak in peaks) {
* Console.Write(count++ + ":" + peak + ", ");
* }
* Console.Write("\n");
*/
// End Testing
// 4: remove peaks that are too close to each other (only want the largest difference per sliding window)
for (int i = windowSize; i <= (rawPoints.Count - windowSize) - 1; i++)
{
if (peaks[i] != 0)
{
// check left side
for (int j = i - windowSize; j < i; j++)
{
if (peaks[j] < peaks[i])
{
peaks[j] = 0;
}
}
// check right side
for (int j = i + 1; j <= i + windowSize; j++)
{
if (peaks[j] < peaks[i])
{
peaks[j] = 0;
}
}
}
}
// Testing
/*
* Console.WriteLine("Peaks after removing nearby peaks:");
* count = 0;
* foreach(float peak in peaks) {
* Console.Write(count++ + ":" + peak + ", ");
* }
* Console.Write("\n");
*/
// End Testing
// 5: create list with the indices of the peaks in the peak vector
// only add the peaks greater than some threshold, this works the same as a naieve algorithm, we only consider it a saccade if the distance is over a vertain threshold.
List <int> peakIndices = new List <int>();
for (int i = 0; i < rawPoints.Count; i++)
{
if (peaks[i] > peakThreshold)
{
peakIndices.Add(i);
}
}
// Testing
/*
* Console.WriteLine("Peak Indices");
* count = 0;
* foreach(float index in peakIndices) {
* Console.Write(count++ + ":" + index + ", ");
* }
* Console.Write("\n");
*/
// End Testing
// 6a: estimate the spacial position of all the fixations between candidate saccades (peaks)
// use the geometric median of all the raw points
// 6b: fixations that are closer together than a specified range are merged together.
// float shortestDistance = 0; // used in 6b
List <Fixation> fixations = new List <Fixation>();
//while(shortestDistance < radius) { // used in 6b
fixations.Clear();
// 6a
for (int i = 1; i <= peakIndices.Count - 1; i++)
{
int rawFromIndex = peakIndices[i - 1];
int rawToIndex = peakIndices[i];
List <GazePoint> points = new List <GazePoint>();
for (int rawIndex = rawFromIndex; rawIndex <= rawToIndex; rawIndex++)
{
points.Add(rawPoints[rawIndex]);
}
VSLocation majorityLocation = MajorityVSLocation(points.ToArray());
Point median = GeometricMedian(ConvertGazePointsToPoints(points));
int startTime = points[0].timestamp;
int endTime = points[points.Count - 1].timestamp;
Fixation fixation = new Fixation(median.x, median.y, startTime, endTime, majorityLocation);
fixations.Add(fixation);
}
// 6b
/*
* shortestDistance = float.MaxValue;
*
* for(int i = 1; i <= fixations.Count - 1; i++) {
*
* int index = 0;
* Point a = new Point(fixations[i - 1].x, fixations[i - 1].y);
* Point b = new Point(fixations[i].x, fixations[i].y);
*
* float distance = EuclideanDistance(a, b);
*
* if(distance < shortestDistance) {
* shortestDistance = distance;
* index = i;
* }
*
* if (shortestDistance < radius) {
* try {
* peakIndices.RemoveAt(index); // BUG: When removing peakIndices, all indices move down a slot, can remove at index and expect all other indices to stay the same...
* }
* catch(Exception e) {
* Console.WriteLine(e.Message);
* Console.WriteLine("index:" + index);
* Console.WriteLine(peakIndices.Count);
* }
* }
* }
* } */
// Testing
/*
* Console.WriteLine("Fixations:");
* count = 0;
* foreach(Fixation fixation in fixations) {
* Console.Write(count++ + ":" + fixation.x + "," + fixation.y + ", ");
* }
* Console.Write("\n");
*/
// End Testing
return(fixations);
}
private Token TokenForFixation(Fixation fixation)
{
return((fixation.endTime - fixation.startTime) < 500 ? Token.Brief : Token.Hold);
}
