public override MtripletsFeature Extract(Bitmap image)
{
var minutiae = MinutiaeExtractor.ExtractFeatures(ImageProvider.AdaptImage(image));
var mtriplets = new List <MTriplet>();
var triplets = new Dictionary <int, int>();
foreach (var triangle in Delaunay2D.Triangulate(minutiae))
{
var idxArr = new[]
{
(short)triangle.A,
(short)triangle.B,
(short)triangle.C
};
var newMTriplet = new MTriplet(idxArr, minutiae);
var newHash = newMTriplet.GetHashCode();
if (!triplets.ContainsKey(newHash))
{
triplets.Add(newHash, 0);
mtriplets.Add(newMTriplet);
}
}
mtriplets.TrimExcess();
return(new MtripletsFeature(mtriplets, minutiae));
}
private double MatchBetaAngles(MTriplet compareTo, byte[] order)
{
var idxArr = new[] { 0, 1, 2, 0 };
double maxdiff = 0;
for (var i = 0; i < 3; i++)
{
var j = idxArr[i + 1];
var qMtiai = Minutiae[MtiaIdxs[i]];
var qMtiaj = Minutiae[MtiaIdxs[j]];
var qbeta = Angle.Difference2Pi(qMtiai.Angle, qMtiaj.Angle);
var tMtiai = compareTo.Minutiae[compareTo.MtiaIdxs[order[i]]];
var tMtiaj = compareTo.Minutiae[compareTo.MtiaIdxs[order[j]]];
var tbeta = Angle.Difference2Pi(tMtiai.Angle, tMtiaj.Angle);
var diff = Angle.DifferencePi(qbeta, tbeta);
if (diff >= AThr)
{
return(0);
}
if (diff > maxdiff)
{
maxdiff = diff;
}
}
return(1 - maxdiff / AThr);
}
public double Match(MTriplet target, out byte[] mtiaOrder)
{
byte[] matchOrder = null;
double maxSimil = 0;
if (Math.Abs(MaxDistance - target.MaxDistance) < DThr &&
Math.Abs(MidDistance - target.MidDistance) < DThr && Math.Abs(MinDistance - target.MinDistance) < DThr)
{
foreach (var order in Orders)
{
var dirSim = MatchMtiaDirections(target, order);
if (dirSim == 0)
{
continue;
}
var distSim = MatchDistances(target, order);
if (distSim == 0)
{
continue;
}
var betaSim = MatchBetaAngles(target, order);
if (betaSim == 0)
{
continue;
}
var alphaSim = MatchAlphaAngles(target, order);
if (alphaSim == 0)
{
continue;
}
var currentSimil = 1 - (1 - distSim) * (1 - alphaSim) * (1 - betaSim);
if (currentSimil > maxSimil)
{
matchOrder = order;
maxSimil = currentSimil;
}
}
}
mtiaOrder = matchOrder;
return(maxSimil);
}
private double MatchMtiaDirections(MTriplet compareTo, byte[] order)
{
double maxdiff = 0;
for (var i = 0; i < 3; i++)
{
var qMtiai = Minutiae[MtiaIdxs[i]];
var tMtiai = compareTo.Minutiae[compareTo.MtiaIdxs[order[i]]];
var diff = Angle.DifferencePi(qMtiai.Angle, tMtiai.Angle);
if (diff >= Math.PI / 4)
{
return(0);
}
if (diff > maxdiff)
{
maxdiff = diff;
}
}
return(1);
}
private double MatchAlphaAngles(MTriplet compareTo, byte[] order)
{
double maxdiff = 0;
for (var i = 0; i < 3; i++)
{
for (var j = 0; j < 3; j++)
{
if (i != j)
{
var qMtiai = Minutiae[MtiaIdxs[i]];
var qMtiaj = Minutiae[MtiaIdxs[j]];
double x = qMtiai.X - qMtiaj.X;
double y = qMtiai.Y - qMtiaj.Y;
var angleij = Angle.ComputeAngle(x, y);
var qAlpha = Angle.Difference2Pi(qMtiai.Angle, angleij);
var tMtiai = compareTo.Minutiae[compareTo.MtiaIdxs[order[i]]];
var tMtiaj = compareTo.Minutiae[compareTo.MtiaIdxs[order[j]]];
x = tMtiai.X - tMtiaj.X;
y = tMtiai.Y - tMtiaj.Y;
angleij = Angle.ComputeAngle(x, y);
var tAlpha = Angle.Difference2Pi(tMtiai.Angle, angleij);
var diff = Angle.DifferencePi(qAlpha, tAlpha);
if (diff >= AThr)
{
return(0);
}
if (diff > maxdiff)
{
maxdiff = diff;
}
}
}
}
return(1 - maxdiff / AThr);
}
private double MatchDistances(MTriplet compareTo, byte[] order)
{
var diff0 = Math.Abs(D[0] - compareTo.D[order[0]]);
if (diff0 > DThr)
{
return(0);
}
var diff1 = Math.Abs(D[1] - compareTo.D[order[1]]);
if (diff1 > DThr)
{
return(0);
}
var diff2 = Math.Abs(D[2] - compareTo.D[order[2]]);
if (diff2 > DThr)
{
return(0);
}
return(1 - Math.Max(diff0, Math.Max(diff1, diff2)) / DThr);
}
internal List <MtripletPair> FindSimilarMTriplets(MTriplet queryMTp)
{
var result = new List <MtripletPair>();
for (var j = 0; j < MTriplets.Count; j++)
{
var currMTp = MTriplets[j];
var currSim = queryMTp.Match(currMTp, out var currOrder);
if (currSim > 0)
{
result.Add(new MtripletPair
{
QueryMTp = queryMTp,
TemplateMTp = currMTp,
MatchingValue = currSim,
TemplateMtiaOrder = currOrder
}
);
}
}
return(result.Count > 0 ? result : null);
}
