/// <summary>
/// Adds a Haar feature node to list
/// </summary>
/// <param name="nodes">List of HaarFeatureNodes</param>
/// <param name="threshold">threshold of node</param>
/// <param name="leftValue">left value</param>
/// <param name="rightValue">right value</param>
/// <param name="rectangles">HaarRectangle</param>
public static void AddHaarFeature(this List<HaarFeatureNode> nodes, double threshold, double leftValue, double rightValue, params HaarRectangle[] rectangles)
{
HaarFeatureNode node = new HaarFeatureNode();
node.Threshold = (float)threshold;
node.LeftValue = (float)leftValue;
node.RightValue = (float)rightValue;
node.RectCount = rectangles.Length;
if (node.RectCount < 2 || node.RectCount > 3) throw new ArgumentException("Haar feature nodes must have 2 or 3 rectangles only");
node.Rect1 = rectangles[0];
node.Rect2 = rectangles[1];
if (node.RectCount > 2) node.Rect3 = rectangles[2];
nodes.Add(node);
}
/// <summary>
/// Detects the presence of an object in a given window.
/// </summary>
protected bool Compute(HaarFeatureNode[] stageNodes,
int stagesCount,
int[] stageNodeCounts, float[] stageThresholds,
IImage2DUIntA integralImage,
IImage2DUIntA integral2Image,
float invArea,
int x, int y, int w, int h)
{
float mean = (float)integralImage.GetIntegralSum(x, y, w, h) * invArea;
float normFactor = (float)integral2Image.GetIntegralSum(x, y, w, h) * invArea
- (mean * mean);
normFactor = (normFactor >= 0) ? (float)Math.Sqrt(normFactor) : 1;
int pos = 0;
for (int j = 0; j < stagesCount; j++)
{
int count = stageNodeCounts[j];
float threshold = stageThresholds[j];
float value = 0;
for (int i = 0; i < count; i++)
{
// evaluate the node's feature
float sum = HaarExtensions.GetNodeSum(ref stageNodes[pos], integralImage, x, y);
// and increase the value accumulator
HaarFeatureNode node = stageNodes[pos++];
value += ((sum < node.Threshold * normFactor) ? node.LeftValue : node.RightValue);
}
if (value <= threshold) return false; // window has been rejected
}
return true;
}
/// <summary>
/// Sets the scale and weight of a Haar-like rectangular feature container.
/// </summary>
public static void SetScaleAndWeight(ref HaarFeatureNode node, float scale, float weight)
{
// manual loop unfolding
if (node.RectCount == 2)
{
ScaleRectangle(ref node.Rect2, scale, weight);
ScaleRectangle(ref node.Rect1, scale, weight);
node.Rect1.ScaledWeight = -(node.Rect2.GetArea() * node.Rect2.ScaledWeight) / node.Rect1.GetArea();
}
else // rectangles.Length == 3
{
ScaleRectangle(ref node.Rect3, scale, weight);
ScaleRectangle(ref node.Rect2, scale, weight);
ScaleRectangle(ref node.Rect1, scale, weight);
node.Rect1.ScaledWeight =
-(node.Rect2.GetArea() * node.Rect2.ScaledWeight + node.Rect3.GetArea() * node.Rect3.ScaledWeight)
/ (node.Rect1.GetArea());
}
}
/// <summary>
/// Gets the sum of the areas of the rectangular features in an integral image.
/// </summary>
public static float GetNodeSum(ref HaarFeatureNode node, IImage2DUIntA integralImage, int x, int y)
{
float sum;
sum = GetSum(ref node.Rect1, integralImage, x, y);
sum += GetSum(ref node.Rect2, integralImage, x, y);
if (node.RectCount == 3) sum += GetSum(ref node.Rect3, integralImage, x, y);
return sum;
}