/// <summary>
/// Utils: Compute the areas of rectangles given two corners.
/// </summary>
private static float AreaOf(FaceDetectionRectangle rect)
{
var h = Clip(rect.Y2 - rect.Y1 + 1, 0);
var w = Clip(rect.X2 - rect.X1 + 1, 0);
return(h * w);
}
/// <summary>
/// PostProcessing.
/// Generates a list of BBox containing the detected face info.
/// </summary>
/// <param name="boundingBoxCollection">empty list of FaceDetectionRec to store results.</param>
/// <param name="scores">score output of Onnx model.</param>
/// <param name="boxes">box output of Onnx model.</param>
/// <param name="scoreThreshold">threshold of score between 0 and 1 for filtering boxes.</param>
private static void GenerateBBox(
ICollection <FaceDetectionRectangle> boundingBoxCollection,
TensorFloat scores, TensorFloat boxes,
float scoreThreshold)
{
IReadOnlyList <float> vectorBoxes = boxes.GetAsVectorView();
IList <float> boxList = vectorBoxes.ToList();
IReadOnlyList <float> vectorScores = scores.GetAsVectorView();
IList <float> scoreList = vectorScores.ToList();
long numAnchors = scores.Shape[1];
if (numAnchors <= 0)
{
return;
}
for (var i = 0; i < numAnchors; i++)
{
if (scoreList[i * 2 + 1] > scoreThreshold)
{
var rect = new FaceDetectionRectangle
{
X1 = boxList[i * 4] * inputImageDataWidth,
Y1 = boxList[i * 4 + 1] * inputImageDataHeight,
X2 = boxList[i * 4 + 2] * inputImageDataWidth,
Y2 = boxList[i * 4 + 3] * inputImageDataHeight,
Score = Clip(scoreList[i * 2 + 1], 0, 1)
};
boundingBoxCollection.Add(rect);
}
}
}
/// <summary>
/// Utils: Return intersection-over-union (Jaccard index) of 2 boxes.
/// </summary>
/// <returns>Float value > 0 if overlapped area exists. -1 if overlapped area doesn't exist.</returns>
private static float IOUOf(FaceDetectionRectangle rect1, FaceDetectionRectangle rect2)
{
var rect = new FaceDetectionRectangle
{
X1 = Math.Max(rect1.X1, rect2.X1),
Y1 = Math.Max(rect1.Y1, rect2.Y1),
X2 = Math.Min(rect1.X2, rect2.X2),
Y2 = Math.Min(rect1.Y2, rect2.Y2),
Score = 0
};
var innerArea = AreaOf(rect);
var area1 = AreaOf(rect1);
var area2 = AreaOf(rect2);
if (innerArea == 0 || area1 == 0 || area2 == 0)
{
return(-1);
}
return(innerArea / (area1 + area2 - innerArea));
}
