private Tuple <TinyFingerprintSchema, TinyFingerprintSchema> GenerateVectors(double similarityIndex, int topWavelets, int length)
{
var random = new Random();
var first = new TinyFingerprintSchema(length);
var second = new TinyFingerprintSchema(length);
var unique = new HashSet <int>();
for (int i = 0; i < topWavelets; ++i)
{
int index = random.Next(length / 2);
if (unique.Contains(2 * index) || unique.Contains(2 * index + 1))
{
i--;
continue;
}
unique.Add(2 * index);
unique.Add(2 * index + 1);
float value = random.NextDouble() > 0.5 ? -1 : 1;
if (random.NextDouble() > similarityIndex)
{
Disagree(value, first, index, second);
}
else
{
Agree(value, first, index, second);
}
}
return(Tuple.Create(first, second));
}
private static void EncodeWavelet(float value, TinyFingerprintSchema array, int index)
{
if (value > 0)
{
array.SetTrueAt(index * 2);
}
else if (value < 0)
{
array.SetTrueAt(index * 2 + 1);
}
}
/// <summary>
/// Encode the integer representation of the fingerprint into a Boolean array
/// </summary>
/// <param name = "concatenated">Concatenated fingerprint (frames concatenated)</param>
/// <param name = "indexes">Sorted indexes with the first one with the highest value in array</param>
/// <param name = "topWavelets">Number of top wavelets to encode</param>
/// <returns>Encoded fingerprint</returns>
public IEncodedFingerprintSchema EncodeFingerprint(float[] concatenated, ushort[] indexes, int topWavelets)
{
TinyFingerprintSchema schema = new TinyFingerprintSchema(concatenated.Length * 2);
for (int i = 0; i < topWavelets; i++)
{
int index = indexes[i];
float value = concatenated[i];
if (value > 0)
{
schema.SetTrueAt(index * 2);
}
else if (value < 0)
{
schema.SetTrueAt((index * 2) + 1);
}
}
return(schema);
}
public static Tuple <TinyFingerprintSchema, TinyFingerprintSchema> GenerateSimilarFingerprints(Random random, double similarityIndex, int topWavelets, int length)
{
var first = new TinyFingerprintSchema(length);
var second = new TinyFingerprintSchema(length);
var indexesTopWavelets = Enumerable.Range(0, length / 2)
.OrderBy(x => random.NextDouble())
.Take(topWavelets);
foreach (int index in indexesTopWavelets)
{
float value = random.NextDouble() > 0.5 ? -1 : 1;
if (random.NextDouble() > similarityIndex)
{
Disagree(value, first, index, second);
}
else
{
Agree(value, first, index, second);
}
}
return(Tuple.Create(first, second));
}
private static void Disagree(float value, TinyFingerprintSchema first, int index, TinyFingerprintSchema second)
{
EncodeWavelet(value, first, index);
EncodeWavelet(-1 * value, second, index);
}
private void Agree(float value, TinyFingerprintSchema first, int index, TinyFingerprintSchema second)
{
EncodeWavelet(value, first, index);
EncodeWavelet(value, second, index);
}
