private void NonMaximumSuppression(List <FaceInfo> input, List <FaceInfo> output, float nmsThreshold = 0.3f, NonMaximumSuppressionMode type = NonMaximumSuppressionMode.Minimum)
{
if (!input.Any())
{
return;
}
input.Sort((f1, f2) => f1.Score.CompareTo(f2.Score));
var nPick = 0;
var vScores = new List <Tuple <float, int> >();
var numBoxes = input.Count;
var vPick = new int[numBoxes];
for (var i = 0; i < numBoxes; ++i)
{
vScores.Add(new Tuple <float, int>(input[i].Score, i));
}
while (vScores.Count > 0)
{
var last = vScores.Last().Item2;
vPick[nPick] = last;
nPick += 1;
for (var index = 0; index < vScores.Count;)
{
var it = vScores[index];
var itemIndex = it.Item2;
var maxX = Math.Max(input[itemIndex].X1, input[last].X1);
var maxY = Math.Max(input[itemIndex].Y1, input[last].Y1);
var minX = Math.Min(input[itemIndex].X2, input[last].X2);
var minY = Math.Min(input[itemIndex].Y2, input[last].Y2);
//maxX1 and maxY1 reuse
maxX = ((minX - maxX + 1) > 0) ? (minX - maxX + 1) : 0;
maxY = ((minY - maxY + 1) > 0) ? (minY - maxY + 1) : 0;
//IOU reuse for the area of two bbox
var iou = maxX * maxY;
switch (type)
{
case NonMaximumSuppressionMode.Union:
iou = iou / (input[itemIndex].Area + input[last].Area - iou);
break;
case NonMaximumSuppressionMode.Minimum:
iou = iou / ((input[itemIndex].Area < input[last].Area) ? input[itemIndex].Area : input[last].Area);
break;
}
if (iou > nmsThreshold)
{
vScores.RemoveAt(index);
}
else
{
index++;
}
}
}
Array.Resize(ref vPick, nPick);
Resize(output, nPick);
for (var i = 0; i < nPick; i++)
{
output[i] = input[vPick[i]];
}
}
private void NonMaximumSuppression(List <FaceInfo> input, ICollection <FaceInfo> output, NonMaximumSuppressionMode type = NonMaximumSuppressionMode.Blending)
{
input.Sort((f1, f2) => f1.Score.CompareTo(f2.Score));
var boxNum = input.Count;
var merged = new int[boxNum];
for (var i = 0; i < boxNum; i++)
{
if (merged[i] > 0)
{
continue;
}
var buf = new List <FaceInfo>
{
input[i]
};
merged[i] = 1;
var h0 = input[i].Y2 - input[i].Y1 + 1;
var w0 = input[i].X2 - input[i].X1 + 1;
var area0 = h0 * w0;
for (var j = i + 1; j < boxNum; j++)
{
if (merged[j] > 0)
{
continue;
}
var innerX0 = input[i].X1 > input[j].X1 ? input[i].X1 : input[j].X1;
var innerY0 = input[i].Y1 > input[j].Y1 ? input[i].Y1 : input[j].Y1;
var innerX1 = input[i].X2 < input[j].X2 ? input[i].X2 : input[j].X2;
var innerY1 = input[i].Y2 < input[j].Y2 ? input[i].Y2 : input[j].Y2;
var innerH = innerY1 - innerY0 + 1;
var innerW = innerX1 - innerX0 + 1;
if (innerH <= 0 || innerW <= 0)
{
continue;
}
var innerArea = innerH * innerW;
var h1 = input[j].Y2 - input[j].Y1 + 1;
var w1 = input[j].X2 - input[j].X1 + 1;
var area1 = h1 * w1;
var score = innerArea / (area0 + area1 - innerArea);
if (score > this._IouThreshold)
{
merged[j] = 1;
buf.Add(input[j]);
}
}
switch (type)
{
case NonMaximumSuppressionMode.Hard:
{
output.Add(buf[0]);
break;
}
case NonMaximumSuppressionMode.Blending:
{
var total = 0d;
for (var j = 0; j < buf.Count; j++)
{
total += Math.Exp(buf[j].Score);
}
var rects = new FaceInfo();
for (var j = 0; j < buf.Count; j++)
{
var rate = Math.Exp(buf[j].Score) / total;
rects.X1 += (float)(buf[j].X1 * rate);
rects.Y1 += (float)(buf[j].Y1 * rate);
rects.X2 += (float)(buf[j].X2 * rate);
rects.Y2 += (float)(buf[j].Y2 * rate);
rects.Score += (float)(buf[j].Score * rate);
}
output.Add(rects);
break;
}
default:
//{
// Console.WriteLine("wrong type of nms.");
// exit(-1);
//}
break;
}
}
#endregion
#endregion
}
