conformalaffine2d_inverse.hpp

#ifndef PASTELMATH_CONFORMALAFFINE2D_INVERSE_H
#define PASTELMATH_CONFORMALAFFINE2D_INVERSE_H

#include "pastel/math/conformalaffine2d/conformalaffine2d_inverse.h"

#include "pastel/sys/math_functions.h"

namespace Pastel
{

    template <typename Real>
    ConformalAffine2D<Real> inverse(
        const ConformalAffine2D<Real>& that)
    {
        // f^-1(x) = (1 / s) Q^T x - (1 / s) Q^T t

        Real invScaling = inverse(that.scaling());

        Real c = std::cos(-that.rotation());
        Real s = std::sin(-that.rotation());
        Real xNew =
            -invScaling * (c * that[0] - s * that[1]); 
        Real yNew =
            -invScaling * (s * that[0] + c * that[1]);

        Vector<Real, N> invTranslation(ofDimension(2));
        invTranslation[0] = xNew;
        invTranslation[1] = yNew;

        ConformalAffine2D<Real> result(
            invScaling,
            -that.rotation(),
            invTranslation);

        return result;
    }

}

#endif