agg_trans_affine.cpp

//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.3
// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
//
// Permission to copy, use, modify, sell and distribute this software 
// is granted provided this copyright notice appears in all copies. 
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
//
//----------------------------------------------------------------------------
// Contact: mcseem@antigrain.com
//          mcseemagg@yahoo.com
//          http://www.antigrain.com
//----------------------------------------------------------------------------
//
// Affine transformations
//
//----------------------------------------------------------------------------
#include "agg_trans_affine.h"



namespace agg
{

    //------------------------------------------------------------------------
    const trans_affine& trans_affine::parl_to_parl(const double* src, 
                                                   const double* dst)
    {
        m0 = src[2] - src[0];
        m1 = src[3] - src[1];
        m2 = src[4] - src[0];
        m3 = src[5] - src[1];
        m4 = src[0];
        m5 = src[1];
        invert();
        multiply(trans_affine(dst[2] - dst[0], dst[3] - dst[1], 
                              dst[4] - dst[0], dst[5] - dst[1],
                              dst[0], dst[1]));
        return *this;
    }

    //------------------------------------------------------------------------
    const trans_affine& trans_affine::rect_to_parl(double x1, double y1, 
                                                   double x2, double y2, 
                                                   const double* parl)
    {
        double src[6];
        src[0] = x1; src[1] = y1;
        src[2] = x2; src[3] = y1;
        src[4] = x2; src[5] = y2;
        parl_to_parl(src, parl);
        return *this;
    }

    //------------------------------------------------------------------------
    const trans_affine& trans_affine::parl_to_rect(const double* parl, 
                                                   double x1, double y1, 
                                                   double x2, double y2)
    {
        double dst[6];
        dst[0] = x1; dst[1] = y1;
        dst[2] = x2; dst[3] = y1;
        dst[4] = x2; dst[5] = y2;
        parl_to_parl(parl, dst);
        return *this;
    }

    //------------------------------------------------------------------------
    const trans_affine& trans_affine::multiply(const trans_affine& m)
    {
        double t0 = m0 * m.m0 + m1 * m.m2;
        double t2 = m2 * m.m0 + m3 * m.m2;
        double t4 = m4 * m.m0 + m5 * m.m2 + m.m4;
        m1 = m0 * m.m1 + m1 * m.m3;
        m3 = m2 * m.m1 + m3 * m.m3;
        m5 = m4 * m.m1 + m5 * m.m3 + m.m5;
        m0 = t0;
        m2 = t2;
        m4 = t4;
        return *this;
    }


    //------------------------------------------------------------------------
    const trans_affine& trans_affine::invert()
    {
        double d  = determinant();

        double t0 =  m3 * d;
               m3 =  m0 * d;
               m1 = -m1 * d;
               m2 = -m2 * d;

        double t4 = -m4 * t0 - m5 * m2;
               m5 = -m4 * m1 - m5 * m3;

        m0 = t0;
        m4 = t4;
        return *this;
    }


   //------------------------------------------------------------------------
    const trans_affine& trans_affine::flip_x()
    {
        m0 = -m0;
        m1 = -m1;
        m4 = -m4;
        return *this;
    }

    //------------------------------------------------------------------------
    const trans_affine& trans_affine::flip_y()
    {
        m2 = -m2;
        m3 = -m3;
        m5 = -m5;
        return *this;
    }

    //------------------------------------------------------------------------
    const trans_affine& trans_affine::reset()
    {
        m0 = m3 = 1.0; 
        m1 = m2 = m4 = m5 = 0.0;
        return *this;
    }

    //------------------------------------------------------------------------
    inline bool is_equal_eps(double v1, double v2, double epsilon)
    {
        return fabs(v1 - v2) < epsilon;
    }

    //------------------------------------------------------------------------
    bool trans_affine::is_identity(double epsilon) const
    {
        return is_equal_eps(m0, 1.0, epsilon) &&
               is_equal_eps(m1, 0.0, epsilon) &&
               is_equal_eps(m2, 0.0, epsilon) && 
               is_equal_eps(m3, 1.0, epsilon) &&
               is_equal_eps(m4, 0.0, epsilon) &&
               is_equal_eps(m5, 0.0, epsilon);
    }

    //------------------------------------------------------------------------
    bool trans_affine::is_equal(const trans_affine& m, double epsilon) const
    {
        return is_equal_eps(m0, m.m0, epsilon) &&
               is_equal_eps(m1, m.m1, epsilon) &&
               is_equal_eps(m2, m.m2, epsilon) && 
               is_equal_eps(m3, m.m3, epsilon) &&
               is_equal_eps(m4, m.m4, epsilon) &&
               is_equal_eps(m5, m.m5, epsilon);
    }

    //------------------------------------------------------------------------
    double trans_affine::rotation() const
    {
        double x1 = 0.0;
        double y1 = 0.0;
        double x2 = 1.0;
        double y2 = 0.0;
        transform(&x1, &y1);
        transform(&x2, &y2);
        return atan2(y2-y1, x2-x1);
    }

    //------------------------------------------------------------------------
    void trans_affine::translation(double* dx, double* dy) const
    {
        trans_affine t(*this);
        t *= trans_affine_rotation(-rotation());
        t.transform(dx, dy);
    }

    //------------------------------------------------------------------------
    void trans_affine::scaling(double* sx, double* sy) const
    {
        double x1 = 0.0;
        double y1 = 0.0;
        double x2 = 1.0;
        double y2 = 1.0;
        trans_affine t(*this);
        t *= trans_affine_rotation(-rotation());
        t.transform(&x1, &y1);
        t.transform(&x2, &y2);
        *sx = x2 - x1;
        *sy = y2 - y1;
    }


}