LinearTransform.h

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/* 
 * LSST Data Management System
 * Copyright 2008-2014 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
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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#ifndef LSST_AFW_GEOM_LINEAR_TRANSFORM_H 
#define LSST_AFW_GEOM_LINEAR_TRANSFORM_H

#include "Eigen/Core"
#include "Eigen/Geometry"
#include "lsst/pex/exceptions/Runtime.h"

#include "lsst/afw/geom/Point.h"
#include "lsst/afw/geom/Angle.h"

namespace lsst {
namespace afw {
namespace geom {

LSST_EXCEPTION_TYPE(SingularTransformException, lsst::pex::exceptions::RuntimeError, lsst::afw::geom::SingularTransformException)


class LinearTransform {
public:
    enum Parameters {XX=0,YX=1,XY=2,YY=3};

    typedef Eigen::Matrix<double,4,1> ParameterVector;
    typedef Eigen::Matrix<double,2,4> TransformDerivativeMatrix;
    typedef Eigen::Matrix<double,4,4> ProductDerivativeMatrix;

    typedef Eigen::Matrix<double,2,2,Eigen::DontAlign> Matrix;

    LinearTransform() : _matrix(Matrix::Identity()) {}

    explicit LinearTransform(Matrix const & matrix) : _matrix(matrix) {}

    LinearTransform operator*(LinearTransform const & other) const {
        return LinearTransform(getMatrix() * other.getMatrix());
    }


    static LinearTransform makeScaling(double s) { 
        return LinearTransform((Matrix() << s, 0.0, 0.0, s).finished());
    }
    
    static LinearTransform makeScaling(double s, double t) { 
        return LinearTransform((Matrix() << s, 0.0, 0.0, t).finished());
    }

    static LinearTransform makeRotation(Angle t) {
        return LinearTransform(Matrix(Eigen::Rotation2D<double>(t.asRadians())));
    }
    
    LinearTransform & operator=(LinearTransform const & other) {
        _matrix = other._matrix;
        return *this;
    }
    
    ParameterVector const getParameterVector() const;
    void setParameterVector(ParameterVector const & vector);
    
    Matrix const & getMatrix() const { return _matrix; }
    Matrix & getMatrix() { return _matrix; }

    double & operator[](int i) { return _matrix(i % 2, i / 2); }
    double const & operator[](int i) const { 
        return const_cast<Matrix&>(_matrix)(i % 2, i / 2);
    }


    LinearTransform const invert() const;
    
    double computeDeterminant() const;

    bool isIdentity() const { return getMatrix().isIdentity(); }

    Point2D operator()(Point2D const & p) const { return Point2D(getMatrix() * p.asEigen()); }

    Extent2D operator()(Extent2D const & p) const { return Extent2D(getMatrix() * p.asEigen()); }

    TransformDerivativeMatrix dTransform(Point2D const & input) const;

    TransformDerivativeMatrix dTransform(Extent2D const & input) const {
        return dTransform(Point2D(input));
    }

private:
    Matrix _matrix;
};

std::ostream & operator<<(std::ostream & os, lsst::afw::geom::LinearTransform const & t);

}}} // namespace lsst::afw::geom

#endif // !LSST_AFW_GEOM_LINEAR_TRANSFORM_H