float ColorHistogram::KLDivergence(const ColorHistogram& rhs) const {
DCHECK(IsNormalized() && rhs.IsNormalized());
const double eps = 1e-10;
return 0.5 * GenericDistance(rhs, [eps](float a, float b) -> float {
const double ratio = (a + eps) / (b + eps);
return a * std::log(ratio) + b * std::log(1.0 / ratio);
});
}
float ColorHistogram::JSDivergence(const ColorHistogram& rhs) const {
DCHECK(IsNormalized() && rhs.IsNormalized());
const double eps = 1e-10;
return 0.5 * GenericDistance(rhs, [eps](float a, float b) -> float {
const double inv_mean = 1.0 / ((a + b) * 0.5 + eps);
const double ratio_a = (a + eps) * inv_mean;
const double ratio_b = (b + eps) * inv_mean;
return a * std::log(ratio_a) + b * std::log(ratio_b);
});
}
float ColorHistogram::ChiSquareDist(const ColorHistogram& rhs) const {
DCHECK(IsNormalized() && rhs.IsNormalized());
return 0.5 * GenericDistance(rhs, [](float a, float b) -> float {
const float add = a + b;
if (fabs(add) > 1e-12) {
const float sub = a - b;
return sub * sub / add;
} else {
return 0.0f;
}
});
}