/// <summary>
/// Applies the non-maximum suppression algorithm to the specified <see cref="Observation"/>s using the
/// specified IOU (intersection over union) threshold and confidence threshold.
/// </summary>
/// <param name="observations">The specified <see cref="Observation"/>s.</param>
/// <param name="iouThreshold">The specified threshold for IOU (intersection over union).</param>
/// <param name="confidenceThreshold">The specified threshold for low-confidence pruning.</param>
/// <returns><see cref="Observation"/>s selected according to the specified thresholds.</returns>
public static IEnumerable <Observation> NonMaximumSuppression(IEnumerable <Observation> observations, double
iouThreshold, double confidenceThreshold)
{
var observationList = observations.ToList();
var sorted = SortObservationsByConfidence(observationList);
var selected = new List <Observation>();
foreach (var observationA in sorted)
{
if (observationA.Confidence < confidenceThreshold)
{
break;
}
var shouldSelect = true;
foreach (var observationB in selected)
{
if (!(SKRectExtensions.IntersectionOverUnion(observationA.BoundingBox, observationB.BoundingBox) >
iouThreshold))
{
continue;
}
shouldSelect = false;
break;
}
if (shouldSelect)
{
selected.Add(observationA);
}
}
return(selected);
}
public void TestIntersectionOverUnion()
{
var rect1 = new SKRect(1f, 2f, 3f, 4f);
var rect2 = new SKRect(2f, 3f, 5f, 7f);
var result = SKRectExtensions.IntersectionOverUnion(rect1, rect2);
Assert.AreEqual(1.0f / 15.0f, result);
}
public void TestUnion_Intersect()
{
var rect1 = new SKRect(1f, 2f, 3f, 4f);
var rect2 = new SKRect(2f, 3f, 5f, 7f);
var result = SKRectExtensions.Union(rect1, rect2);
Assert.AreEqual(15.0f, result, Tolerance);
}
