agg_rasterizer_scanline_aa.h

okular

//----------------------------------------------------------------------------
// 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.
//
// The author gratefully acknowleges the support of David Turner, 
// Robert Wilhelm, and Werner Lemberg - the authors of the FreeType 
// libray - in producing this work. See http://www.freetype.org for details.
//
//----------------------------------------------------------------------------
// Contact: [e-mail]
//          [e-mail]
//          http://www.antigrain.com
//----------------------------------------------------------------------------
//
// Class rasterizer_scanline_aa
//         
//
//----------------------------------------------------------------------------
#ifndef AGG_RASTERIZER_SCANLINE_AA_INCLUDED
#define AGG_RASTERIZER_SCANLINE_AA_INCLUDED

#include <string.h>
#include <math.h>
#include "agg_basics.h"
#include "agg_math.h"
#include "agg_gamma_functions.h"
#include "agg_clip_liang_barsky.h"
#include "agg_render_scanlines.h"


namespace agg
{

    //------------------------------------------------------------------------
    // These constants determine the subpixel accuracy, to be more precise, 
    // the number of bits of the fractional part of the coordinates. 
    // The possible coordinate capacity in bits can be calculated by formula:
    // sizeof(int) * 8 - poly_base_shift * 2, i.e, for 32-bit integers and
    // 8-bits fractional part the capacity is 16 bits or [-32768...32767].
    enum
    {
        poly_base_shift = 8,                       //----poly_base_shift
        poly_base_size  = 1 << poly_base_shift,    //----poly_base_size 
        poly_base_mask  = poly_base_size - 1       //----poly_base_mask 
    };
    
    //--------------------------------------------------------------poly_coord
    inline int poly_coord(double c)
    {
        return int(c * poly_base_size);
    }

    //-----------------------------------------------------------------cell_aa
    // A pixel cell. There're no constructors defined and it was done 
    // intentionally in order to avoid extra overhead when allocating an 
    // array of cells.
    struct cell_aa
    {
        int16 x;
        int16 y;
        int   packed_coord;
        int   cover;
        int   area;

        void set(int x, int y, int c, int a);
        void set_coord(int x, int y);
        void set_cover(int c, int a);
        void add_cover(int c, int a);
    };


    //--------------------------------------------------------------outline_aa
    // An internal class that implements the main rasterization algorithm.
    // Used in the rasterizer. Should not be used direcly.
    class outline_aa
    {
        enum
        {
            cell_block_shift = 12,
            cell_block_size  = 1 << cell_block_shift,
            cell_block_mask  = cell_block_size - 1,
            cell_block_pool  = 256,
            cell_block_limit = 1024
        };

    public:

        ~outline_aa();
        outline_aa();

        void reset();

        void move_to(int x, int y);
        void line_to(int x, int y);

        int min_x() const { return m_min_x; }
        int min_y() const { return m_min_y; }
        int max_x() const { return m_max_x; }
        int max_y() const { return m_max_y; }

        const cell_aa* const* cells();
        unsigned num_cells() { cells(); return m_num_cells; }
        bool sorted() const { return m_sorted; }

    private:
        outline_aa(const outline_aa&);
        const outline_aa& operator = (const outline_aa&);

        void set_cur_cell(int x, int y);
        void add_cur_cell();
        void sort_cells();
        void render_hline(int ey, int x1, int y1, int x2, int y2);
        void render_line(int x1, int y1, int x2, int y2);
        void allocate_block();
        
        static void qsort_cells(cell_aa** start, unsigned num);

    private:
        unsigned  m_num_blocks;
        unsigned  m_max_blocks;
        unsigned  m_cur_block;
        unsigned  m_num_cells;
        cell_aa** m_cells;
        cell_aa*  m_cur_cell_ptr;
        cell_aa** m_sorted_cells;
        unsigned  m_sorted_size;
        cell_aa   m_cur_cell;
        int       m_cur_x;
        int       m_cur_y;
        int       m_min_x;
        int       m_min_y;
        int       m_max_x;
        int       m_max_y;
        bool      m_sorted;
    };


    //----------------------------------------------------------filling_rule_e
    enum filling_rule_e
    {
        fill_non_zero,
        fill_even_odd
    };


    //==================================================rasterizer_scanline_aa
    // Polygon rasterizer that is used to render filled polygons with 
    // high-quality Anti-Aliasing. Internally, by default, the class uses 
    // integer coordinates in format 24.8, i.e. 24 bits for integer part 
    // and 8 bits for fractional - see poly_base_shift. This class can be 
    // used in the following  way:
    //
    // 1. filling_rule(filling_rule_e ft) - optional.
    //
    // 2. gamma() - optional.
    //
    // 3. reset()
    //
    // 4. move_to(x, y) / line_to(x, y) - make the polygon. One can create 
    //    more than one contour, but each contour must consist of at least 3
    //    vertices, i.e. move_to(x1, y1); line_to(x2, y2); line_to(x3, y3);
    //    is the absolute minimum of vertices that define a triangle.
    //    The algorithm does not check either the number of vertices nor
    //    coincidence of their coordinates, but in the worst case it just 
    //    won't draw anything.
    //    The orger of the vertices (clockwise or counterclockwise) 
    //    is important when using the non-zero filling rule (fill_non_zero).
    //    In this case the vertex order of all the contours must be the same
    //    if you want your intersecting polygons to be without "holes".
    //    You actually can use different vertices order. If the contours do not 
    //    intersect each other the order is not important anyway. If they do, 
    //    contours with the same vertex order will be rendered without "holes" 
    //    while the intersecting contours with different orders will have "holes".
    //
    // filling_rule() and gamma() can be called anytime before "sweeping".
    //------------------------------------------------------------------------
    template<unsigned XScale=1, unsigned AA_Shift=8> class rasterizer_scanline_aa
    {
        enum status
        {
            status_initial,
            status_line_to,
            status_closed
        };

        struct iterator
        {
            const cell_aa* const* cells;
            int                   cover;
            int                   last_y;
        };

    public:
        enum
        {
            aa_shift = AA_Shift,
            aa_num   = 1 << aa_shift,
            aa_mask  = aa_num - 1,
            aa_2num  = aa_num * 2,
            aa_2mask = aa_2num - 1
        };

        //--------------------------------------------------------------------
        rasterizer_scanline_aa() : 
            m_filling_rule(fill_non_zero),
            m_clipped_start_x(0),
            m_clipped_start_y(0),
            m_start_x(0),
            m_start_y(0),
            m_prev_x(0),
            m_prev_y(0),
            m_prev_flags(0),
            m_status(status_initial),
            m_clipping(false)
        {
            int i;
            for(i = 0; i < aa_num; i++) m_gamma[i] = i;
        }

        //--------------------------------------------------------------------
        template<class GammaF> 
        rasterizer_scanline_aa(const GammaF& gamma_function) : 
            m_filling_rule(fill_non_zero),
            m_clipped_start_x(0),
            m_clipped_start_y(0),
            m_start_x(0),
            m_start_y(0),
            m_prev_x(0),
            m_prev_y(0),
            m_prev_flags(0),
            m_status(status_initial),
            m_clipping(false)
        {
            gamma(gamma_function);
        }

        //--------------------------------------------------------------------
        void reset(); 
        void filling_rule(filling_rule_e filling_rule);
        void clip_box(double x1, double y1, double x2, double y2);
        void reset_clipping();

        //--------------------------------------------------------------------
        template<class GammaF> void gamma(const GammaF& gamma_function)
        { 
            int i;
            for(i = 0; i < aa_num; i++)
            {
                m_gamma[i] = int(floor(gamma_function(double(i) / aa_mask) * aa_mask + 0.5));
            }
        }

        //--------------------------------------------------------------------
        unsigned apply_gamma(unsigned cover) const 
        { 
            return m_gamma[cover]; 
        }

        //--------------------------------------------------------------------
        void add_vertex(double x, double y, unsigned cmd);
        void move_to(int x, int y);
        void line_to(int x, int y);
        void close_polygon();
        void move_to_d(double x, double y);
        void line_to_d(double x, double y);
        
        //--------------------------------------------------------------------
        int min_x() const { return m_outline.min_x(); }
        int min_y() const { return m_outline.min_y(); }
        int max_x() const { return m_outline.max_x(); }
        int max_y() const { return m_outline.max_y(); }

        //--------------------------------------------------------------------
        AGG_INLINE unsigned calculate_alpha(int area) const
        {
            int cover = area >> (poly_base_shift*2 + 1 - aa_shift);

            if(cover < 0) cover = -cover;
            if(m_filling_rule == fill_even_odd)
            {
                cover &= aa_2mask;
                if(cover > aa_num)
                {
                    cover = aa_2num - cover;
                }
            }
            if(cover > aa_mask) cover = aa_mask;
            return m_gamma[cover];
        }

        //--------------------------------------------------------------------
        void sort()
        {
            m_outline.cells();
        }


        //--------------------------------------------------------------------
        bool rewind_scanlines()
        {
            close_polygon();
            m_iterator.cells = m_outline.cells();
            if(m_outline.num_cells() == 0) 
            {
                return false;
            }
            m_iterator.cover  = 0;
            m_iterator.last_y = (*m_iterator.cells)->y;
            return true;
        }


        //--------------------------------------------------------------------
        template<class Scanline> bool sweep_scanline(Scanline& sl)
        {
            sl.reset_spans();
            for(;;)
            {
                const cell_aa* cur_cell = *m_iterator.cells;
                if(cur_cell == 0) return false;
                ++m_iterator.cells;
                m_iterator.last_y = cur_cell->y;

                for(;;)
                {
                    int coord  = cur_cell->packed_coord;
                    int area   = cur_cell->area; 
                    int last_x = cur_cell->x;

                    m_iterator.cover += cur_cell->cover;

                    //accumulate all cells with the same coordinates
                    for(; (cur_cell = *m_iterator.cells) != 0; ++m_iterator.cells)
                    {
                        if(cur_cell->packed_coord != coord) break;
                        area             += cur_cell->area;
                        m_iterator.cover += cur_cell->cover;
                    }

                    int alpha;
                    if(cur_cell == 0 || cur_cell->y != m_iterator.last_y)
                    {

                        if(area)
                        {
                            alpha = calculate_alpha((m_iterator.cover << (poly_base_shift + 1)) - area);
                            if(alpha)
                            {
                                sl.add_cell(last_x, alpha);
                            }
                            ++last_x;
                        }
                        break;
                    }

                    ++m_iterator.cells;

                    if(area)
                    {
                        alpha = calculate_alpha((m_iterator.cover << (poly_base_shift + 1)) - area);
                        if(alpha)
                        {
                            sl.add_cell(last_x, alpha);
                        }
                        ++last_x;
                    }