agg_math_stroke.h

windows ce 下的画各种b样条曲线

//----------------------------------------------------------------------------
// Anti-Grain Geometry (AGG) - Version 2.5
// A high quality rendering engine for C++
// Copyright (C) 2002-2006 Maxim Shemanarev
// Contact: [e-mail]
//          [e-mail]
//          http://antigrain.com
// 
// AGG is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
// 
// AGG is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with AGG; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, 
// MA 02110-1301, USA.
//----------------------------------------------------------------------------

#ifndef AGG_STROKE_MATH_INCLUDED
#define AGG_STROKE_MATH_INCLUDED

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

namespace agg
{
    //-------------------------------------------------------------line_cap_e
    enum line_cap_e
    {
        butt_cap,
        square_cap,
        round_cap
    };

    //------------------------------------------------------------line_join_e
    enum line_join_e
    {
        miter_join         = 0,
        miter_join_revert  = 1,
        round_join         = 2,
        bevel_join         = 3,
        miter_join_round   = 4
    };


    //-----------------------------------------------------------inner_join_e
    enum inner_join_e
    {
        inner_bevel,
        inner_miter,
        inner_jag,
        inner_round
    };

    //------------------------------------------------------------math_stroke
    template<class VertexConsumer> class math_stroke
    {
    public:
        typedef typename VertexConsumer::value_type coord_type;

        math_stroke();

        void line_cap(line_cap_e lc)     { m_line_cap = lc; }
        void line_join(line_join_e lj)   { m_line_join = lj; }
        void inner_join(inner_join_e ij) { m_inner_join = ij; }

        line_cap_e   line_cap()   const { return m_line_cap; }
        line_join_e  line_join()  const { return m_line_join; }
        inner_join_e inner_join() const { return m_inner_join; }

        void width(double w);
        void miter_limit(double ml) { m_miter_limit = ml; }
        void miter_limit_theta(double t);
        void inner_miter_limit(double ml) { m_inner_miter_limit = ml; }
        void approximation_scale(double as) { m_approx_scale = as; }

        double width() const { return m_width * 2.0; }
        double miter_limit() const { return m_miter_limit; }
        double inner_miter_limit() const { return m_inner_miter_limit; }
        double approximation_scale() const { return m_approx_scale; }

        void calc_cap(VertexConsumer& vc,
                      const vertex_dist& v0, 
                      const vertex_dist& v1, 
                      double len);

        void calc_join(VertexConsumer& vc,
                       const vertex_dist& v0, 
                       const vertex_dist& v1, 
                       const vertex_dist& v2,
                       double len1, 
                       double len2);

    private:
        AGG_INLINE void add_vertex(VertexConsumer& vc, double x, double y)
        {
            vc.add(coord_type(x, y));
        }

        void calc_arc(VertexConsumer& vc,
                      double x,   double y, 
                      double dx1, double dy1, 
                      double dx2, double dy2);

        void calc_miter(VertexConsumer& vc,
                        const vertex_dist& v0, 
                        const vertex_dist& v1, 
                        const vertex_dist& v2,
                        double dx1, double dy1, 
                        double dx2, double dy2,
                        line_join_e lj,
                        double mlimit,
                        double dbevel);

        double       m_width;
        double       m_width_abs;
        double       m_width_eps;
        int          m_width_sign;
        double       m_miter_limit;
        double       m_inner_miter_limit;
        double       m_approx_scale;
        line_cap_e   m_line_cap;
        line_join_e  m_line_join;
        inner_join_e m_inner_join;
    };

    //-----------------------------------------------------------------------
    template<class VC> math_stroke<VC>::math_stroke() :
        m_width(0.5),
        m_width_abs(0.5),
        m_width_eps(0.5/1024.0),
        m_width_sign(1),
        m_miter_limit(4.0),
        m_inner_miter_limit(1.01),
        m_approx_scale(1.0),
        m_line_cap(butt_cap),
        m_line_join(miter_join),
        m_inner_join(inner_miter)
    {
    }

    //-----------------------------------------------------------------------
    template<class VC> void math_stroke<VC>::width(double w)
    { 
        m_width = w * 0.5; 
        if(m_width < 0)
        {
            m_width_abs  = -m_width;
            m_width_sign = -1;
        }
        else
        {
            m_width_abs  = m_width;
            m_width_sign = 1;
        }
        m_width_eps = m_width / 1024.0;
    }

    //-----------------------------------------------------------------------
    template<class VC> void math_stroke<VC>::miter_limit_theta(double t)
    { 
        m_miter_limit = 1.0 / sin(t * 0.5) ;
    }

    //-----------------------------------------------------------------------
    template<class VC> 
    void math_stroke<VC>::calc_arc(VC& vc,
                                   double x,   double y, 
                                   double dx1, double dy1, 
                                   double dx2, double dy2)
    {
        double a1 = atan2(dy1 * m_width_sign, dx1 * m_width_sign);
        double a2 = atan2(dy2 * m_width_sign, dx2 * m_width_sign);
        double da = a1 - a2;
        int i, n;

        da = acos(m_width_abs / (m_width_abs + 0.125 / m_approx_scale)) * 2;

        add_vertex(vc, x + dx1, y + dy1);
        if(m_width_sign > 0)
        {
            if(a1 > a2) a2 += 2 * pi;
            n = int((a2 - a1) / da);
            da = (a2 - a1) / (n + 1);
            a1 += da;
            for(i = 0; i < n; i++)
            {
                add_vertex(vc, x + cos(a1) * m_width, y + sin(a1) * m_width);
                a1 += da;
            }
        }
        else
        {
            if(a1 < a2) a2 -= 2 * pi;
            n = int((a1 - a2) / da);
            da = (a1 - a2) / (n + 1);
            a1 -= da;
            for(i = 0; i < n; i++)
            {
                add_vertex(vc, x + cos(a1) * m_width, y + sin(a1) * m_width);
                a1 -= da;
            }
        }
        add_vertex(vc, x + dx2, y + dy2);
    }

    //-----------------------------------------------------------------------
    template<class VC> 
    void math_stroke<VC>::calc_miter(VC& vc,
                                     const vertex_dist& v0, 
                                     const vertex_dist& v1, 
                                     const vertex_dist& v2,
                                     double dx1, double dy1, 
                                     double dx2, double dy2,
                                     line_join_e lj,
                                     double mlimit,
                                     double dbevel)
    {
        double xi  = v1.x;
        double yi  = v1.y;
        double di  = 1;
        double lim = m_width_abs * mlimit;
        bool miter_limit_exceeded = true; // Assume the worst
        bool intersection_failed  = true; // Assume the worst

        if(calc_intersection(v0.x + dx1, v0.y - dy1,
                             v1.x + dx1, v1.y - dy1,
                             v1.x + dx2, v1.y - dy2,
                             v2.x + dx2, v2.y - dy2,
                             &xi, &yi))
        {
            // Calculation of the intersection succeeded
            //---------------------
            di = calc_distance(v1.x, v1.y, xi, yi);
            if(di <= lim)
            {
                // Inside the miter limit
                //---------------------
                add_vertex(vc, xi, yi);
                miter_limit_exceeded = false;
            }
            intersection_failed = false;
        }
        else
        {
            // Calculation of the intersection failed, most probably
            // the three points lie one straight line. 
            // First check if v0 and v2 lie on the opposite sides of vector: 
            // (v1.x, v1.y) -> (v1.x+dx1, v1.y-dy1), that is, the perpendicular
            // to the line determined by vertices v0 and v1.
            // This condition determines whether the next line segments continues
            // the previous one or goes back.
            //----------------
            double x2 = v1.x + dx1;
            double y2 = v1.y - dy1;
            if((cross_product(v0.x, v0.y, v1.x, v1.y, x2, y2) < 0.0) == 
               (cross_product(v1.x, v1.y, v2.x, v2.y, x2, y2) < 0.0))
            {
                // This case means that the next segment continues 
                // the previous one (straight line)