mapnik/deps/agg/src/agg_trans_single_path.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
//----------------------------------------------------------------------------

#include "agg_math.h"
#include "agg_vertex_sequence.h"
#include "agg_trans_single_path.h"

namespace agg
{

//------------------------------------------------------------------------
trans_single_path::trans_single_path() :
    m_base_length(0.0),
    m_kindex(0.0),
    m_status(initial),
    m_preserve_x_scale(true)
{
}

//------------------------------------------------------------------------
void trans_single_path::reset()
{
    m_src_vertices.remove_all();
    m_kindex = 0.0;
    m_status = initial;
}

//------------------------------------------------------------------------
void trans_single_path::move_to(double x, double y)
{
    if(m_status == initial)
    {
        m_src_vertices.modify_last(vertex_dist(x, y));
        m_status = making_path;
    }
    else
    {
        line_to(x, y);
    }
}

//------------------------------------------------------------------------
void trans_single_path::line_to(double x, double y)
{
    if(m_status == making_path)
    {
        m_src_vertices.add(vertex_dist(x, y));
    }
}


//------------------------------------------------------------------------
void trans_single_path::finalize_path()
{
    if(m_status == making_path && m_src_vertices.size() > 1)
    {
        unsigned i;
        double dist;
        double d;

        m_src_vertices.close(false);
        if(m_src_vertices.size() > 2)
        {
            if(m_src_vertices[m_src_vertices.size() - 2].dist * 10.0 <
               m_src_vertices[m_src_vertices.size() - 3].dist)
            {
                d = m_src_vertices[m_src_vertices.size() - 3].dist +
                    m_src_vertices[m_src_vertices.size() - 2].dist;

                m_src_vertices[m_src_vertices.size() - 2] =
                    m_src_vertices[m_src_vertices.size() - 1];

                m_src_vertices.remove_last();
                m_src_vertices[m_src_vertices.size() - 2].dist = d;
            }
        }

        dist = 0.0;
        for(i = 0; i < m_src_vertices.size(); i++)
        {
            vertex_dist& v = m_src_vertices[i];
            double d = v.dist;
            v.dist = dist;
            dist += d;
        }
        m_kindex = (m_src_vertices.size() - 1) / dist;
        m_status = ready;
    }
}



//------------------------------------------------------------------------
double trans_single_path::total_length() const
{
    if(m_base_length >= 1e-10) return m_base_length;
    return (m_status == ready) ?
        m_src_vertices[m_src_vertices.size() - 1].dist :
        0.0;
}


//------------------------------------------------------------------------
void trans_single_path::transform(double *x, double *y) const
{
    if(m_status == ready)
    {
        if(m_base_length > 1e-10)
        {
            *x *= m_src_vertices[m_src_vertices.size() - 1].dist /
                m_base_length;
        }

        double x1 = 0.0;
        double y1 = 0.0;
        double dx = 1.0;
        double dy = 1.0;
        double d  = 0.0;
        double dd = 1.0;
        if(*x < 0.0)
        {
            // Extrapolation on the left
            //--------------------------
            x1 = m_src_vertices[0].x;
            y1 = m_src_vertices[0].y;
            dx = m_src_vertices[1].x - x1;
            dy = m_src_vertices[1].y - y1;
            dd = m_src_vertices[1].dist - m_src_vertices[0].dist;
            d  = *x;
        }
        else
            if(*x > m_src_vertices[m_src_vertices.size() - 1].dist)
            {
                // Extrapolation on the right
                //--------------------------
                unsigned i = m_src_vertices.size() - 2;
                unsigned j = m_src_vertices.size() - 1;
                x1 = m_src_vertices[j].x;
                y1 = m_src_vertices[j].y;
                dx = x1 - m_src_vertices[i].x;
                dy = y1 - m_src_vertices[i].y;
                dd = m_src_vertices[j].dist - m_src_vertices[i].dist;
                d  = *x - m_src_vertices[j].dist;
            }
            else
            {
                // Interpolation
                //--------------------------
                unsigned i = 0;
                unsigned j = m_src_vertices.size() - 1;
                if(m_preserve_x_scale)
                {
                    unsigned k;
                    for(i = 0; (j - i) > 1; )
                    {
                        if(*x < m_src_vertices[k = (i + j) >> 1].dist)
                        {
                            j = k;
                        }
                        else
                        {
                            i = k;
                        }
                    }
                    d  = m_src_vertices[i].dist;
                    dd = m_src_vertices[j].dist - d;
                    d  = *x - d;
                }
                else
                {
                    i = unsigned(*x * m_kindex);
                    j = i + 1;
                    dd = m_src_vertices[j].dist - m_src_vertices[i].dist;
                    d = ((*x * m_kindex) - i) * dd;
                }
                x1 = m_src_vertices[i].x;
                y1 = m_src_vertices[i].y;
                dx = m_src_vertices[j].x - x1;
                dy = m_src_vertices[j].y - y1;
            }
        double x2 = x1 + dx * d / dd;
        double y2 = y1 + dy * d / dd;
        *x = x2 - *y * dy / dd;
        *y = y2 + *y * dx / dd;
    }
}


}