ReducedShear.cc

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// -*- lsst-c++ -*-
 
/*
 * LSST Data Management System
 * Copyright 2008, 2009, 2010 LSST Corporation.
 *
 * This product includes software developed by the
 * LSST Project (http://www.lsst.org/).
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
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#include "lsst/afw/geom/ellipses/ReducedShear.h"
#include "lsst/afw/geom/ellipses/ConformalShear.h"
#include "lsst/afw/geom/ellipses/Distortion.h"
 
namespace lsst {
namespace afw {
namespace geom {
namespace ellipses {
 
double ReducedShear::getAxisRatio() const {
    double e = getE();
    return (1.0 - e) / (1.0 + e);
}
 
ReducedShear& ReducedShear::operator=(Distortion const& other) {
    double delta = other.getE();
    if (delta < 1E-8) {
        _complex = other.getComplex() * (0.5 + 0.125 * delta * delta);
    } else {
        double g = (1.0 - std::sqrt(1.0 - delta * delta)) / delta;
        _complex = other.getComplex() * g / delta;
    }
    return *this;
}
 
ReducedShear& ReducedShear::operator=(ConformalShear const& other) {
    double eta = other.getE();
    if (eta < 1E-8) {
        _complex = other.getComplex() * (0.5 - eta * eta / 12.0);
    } else {
        double g = std::tanh(0.5 * eta);
        _complex = other.getComplex() * g / eta;
    }
    return *this;
}
 
detail::EllipticityBase::Jacobian ReducedShear::dAssign(Distortion const& other) {
    Jacobian result = Jacobian::Zero();
    double delta = other.getE();
    double s = std::sqrt(1.0 - delta * delta);
    double alpha, beta;
    if (delta < 1E-8) {
        alpha = 0.5 + 0.125 * delta * delta;
        beta = 0.25;
    } else {
        alpha = (1.0 - s) / (delta * delta);
        beta = (2.0 * alpha - 1.0) / (delta * delta * s);
    }
    _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 ReducedShear::dAssign(ConformalShear const& other) {
    Jacobian result = Jacobian::Zero();
    double eta = other.getE();
    double alpha, beta;
    if (eta < 1E-8) {
        alpha = 0.5 - eta * eta / 24.0;
        beta = -1.0 / 12;
    } else {
        double g = std::tanh(0.5 * eta);
        alpha = g / eta;
        beta = (0.5 * (1.0 - g * g) - 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;
}
}  // namespace ellipses
}  // namespace geom
}  // namespace afw
}  // namespace lsst