mapnik/deps/agg/src/agg_trans_affine.cpp

//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.4
// 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::identity;

//------------------------------------------------------------------------
const trans_affine& trans_affine::parl_to_parl(const double* src,
                                               const double* dst)
{
    sx  = src[2] - src[0];
    shy = src[3] - src[1];
    shx = src[4] - src[0];
    sy  = src[5] - src[1];
    tx  = src[0];
    ty  = 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 = sx  * m.sx + shy * m.shx;
    double t2 = shx * m.sx + sy  * m.shx;
    double t4 = tx  * m.sx + ty  * m.shx + m.tx;
    shy = sx  * m.shy + shy * m.sy;
    sy  = shx * m.shy + sy  * m.sy;
    ty  = tx  * m.shy + ty  * m.sy + m.ty;
    sx  = t0;
    shx = t2;
    tx  = t4;
    return *this;
}


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

    double t0  =  sy  * d;
    sy  =  sx  * d;
    shy = -shy * d;
    shx = -shx * d;

    double t4 = -tx * t0  - ty * shx;
    ty = -tx * shy - ty * sy;

    sx = t0;
    tx = t4;
    return *this;
}


//------------------------------------------------------------------------
const trans_affine& trans_affine::flip_x()
{
    sx  = -sx;
    shy = -shy;
    tx  = -tx;
    return *this;
}

//------------------------------------------------------------------------
const trans_affine& trans_affine::flip_y()
{
    shx = -shx;
    sy  = -sy;
    ty  = -ty;
    return *this;
}

//------------------------------------------------------------------------
const trans_affine& trans_affine::reset()
{
    sx  = sy  = 1.0;
    shy = shx = tx = ty = 0.0;
    return *this;
}

//------------------------------------------------------------------------
bool trans_affine::is_identity(double epsilon) const
{
    return is_equal_eps(sx,  1.0, epsilon) &&
        is_equal_eps(shy, 0.0, epsilon) &&
        is_equal_eps(shx, 0.0, epsilon) &&
        is_equal_eps(sy,  1.0, epsilon) &&
        is_equal_eps(tx,  0.0, epsilon) &&
        is_equal_eps(ty,  0.0, epsilon);
}

//------------------------------------------------------------------------
bool trans_affine::is_valid(double epsilon) const
{
    return std::fabs(sx) > epsilon && std::fabs(sy) > epsilon;
}

//------------------------------------------------------------------------
bool trans_affine::is_equal(const trans_affine& m, double epsilon) const
{
    return is_equal_eps(sx,  m.sx,  epsilon) &&
        is_equal_eps(shy, m.shy, epsilon) &&
        is_equal_eps(shx, m.shx, epsilon) &&
        is_equal_eps(sy,  m.sy,  epsilon) &&
        is_equal_eps(tx,  m.tx,  epsilon) &&
        is_equal_eps(ty,  m.ty,  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 std::atan2(y2-y1, x2-x1);
}

//------------------------------------------------------------------------
void trans_affine::translation(double* dx, double* dy) const
{
    *dx = tx;
    *dy = ty;
}

//------------------------------------------------------------------------
void trans_affine::scaling(double* x, double* y) 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);
    *x = x2 - x1;
    *y = y2 - y1;
}


}