Distortion.cc

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// -*- lsst-c++ -*-

/*
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 * Copyright 2008, 2009, 2010 LSST Corporation.
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#include "lsst/afw/geom/ellipses/Distortion.h"
#include "lsst/afw/geom/ellipses/ReducedShear.h"
#include "lsst/afw/geom/ellipses/ConformalShear.h"
#include "lsst/afw/geom/ellipses/BaseCore.h"

namespace lsst {
namespace afw {
namespace geom {
namespace ellipses {

double Distortion::getAxisRatio() const {
    double e = getE();
    return std::sqrt((1.0 - e) / (1.0 + e));
}

Distortion& Distortion::operator=(ConformalShear const& other) {
    double eta = other.getE();
    if (eta < 1E-8) {
        _complex = other.getComplex() * (1.0 - eta * eta / 3.0);
    } else {
        double delta = std::tanh(eta);
        _complex = other.getComplex() * delta / eta;
    }
    return *this;
}

Distortion& Distortion::operator=(ReducedShear const& other) {
    double g = other.getE();
    _complex = other.getComplex() * 2.0 / (1 + g * g);
    return *this;
}

detail::EllipticityBase::Jacobian Distortion::dAssign(ConformalShear const& other) {
    Jacobian result = Jacobian::Zero();
    double eta = other.getE();
    double alpha, beta;
    if (eta < 1E-8) {
        alpha = (1.0 - eta * eta / 3.0);
        beta = -2.0 / 3.0;
    } else {
        double delta = std::tanh(eta);
        alpha = delta / eta;
        beta = (1.0 - delta * delta - alpha) / (eta * eta);
    }
    _complex = other.getComplex() * alpha;
    result(0, 0) = alpha + other.getE1() * other.getE1() * beta;
    result(1, 1) = alpha + other.getE2() * other.getE2() * beta;
    result(1, 0) = result(0, 1) = other.getE1() * other.getE2() * beta;
    return result;
}

detail::EllipticityBase::Jacobian Distortion::dAssign(ReducedShear const& other) {
    Jacobian result = Jacobian::Zero();
    double g = other.getE();
    double alpha = 2.0 / (1 + g * g);
    double beta = -alpha * alpha;
    _complex = other.getComplex() * alpha;
    result(0, 0) = alpha + other.getE1() * other.getE1() * beta;
    result(1, 1) = alpha + other.getE2() * other.getE2() * beta;
    result(1, 0) = result(0, 1) = other.getE1() * other.getE2() * beta;
    return result;
}

void Distortion::normalize() {
    if (getE() > 1.0) {
        throw LSST_EXCEPT(lsst::pex::exceptions::InvalidParameterError,
                          "Distortion magnitude cannot be greater than one.");
    }
}
}  // namespace ellipses
}  // namespace geom
}  // namespace afw
}  // namespace lsst