agg_scanline_boolean_algebra.h

来自「这是VCF框架的代码」· C头文件 代码 · 共 1,568 行 · 第 1/4 页

        {
            unsigned k = a * b;
            if(k == cover_mask * cover_mask) return 0;

            a = (cover_mask * cover_mask - (a << cover_shift) + k) >> cover_shift;
            b = (cover_mask * cover_mask - (b << cover_shift) + k) >> cover_shift;
            return cover_mask - ((a * b) >> cover_shift);
        }
    };


    //-------------------------------------------sbool_xor_formula_abs_diff
    struct sbool_xor_formula_abs_diff
    {
        static AGG_INLINE unsigned calculate(unsigned a, unsigned b)
        {
            return unsigned(abs(int(a) - int(b)));
        }
    };



    //----------------------------------------------------sbool_xor_spans_aa
    // Functor.
    // XOR two spans preserving the anti-aliasing information.
    // The result is added to the "sl" scanline.
    //------------------
    template<class Scanline1, 
             class Scanline2, 
             class Scanline, 
             class XorFormula,
             unsigned CoverShift = cover_shift> 
    struct sbool_xor_spans_aa
    {
        enum cover_scale_e
        {
            cover_shift = CoverShift,
            cover_size  = 1 << cover_shift,
            cover_mask  = cover_size - 1,
            cover_full  = cover_mask
        };
        

        void operator () (const typename Scanline1::const_iterator& span1, 
                          const typename Scanline2::const_iterator& span2, 
                          int x, unsigned len, 
                          Scanline& sl) const
        {
            unsigned cover;
            const typename Scanline1::cover_type* covers1;
            const typename Scanline2::cover_type* covers2;

            // Calculate the operation code and choose the 
            // proper combination algorithm.
            // 0 = Both spans are of AA type
            // 1 = span1 is solid, span2 is AA
            // 2 = span1 is AA, span2 is solid
            // 3 = Both spans are of solid type
            //-----------------
            switch((span1->len < 0) | ((span2->len < 0) << 1))
            {
            case 0:      // Both are AA spans
                covers1 = span1->covers;
                covers2 = span2->covers;
                if(span1->x < x) covers1 += x - span1->x;
                if(span2->x < x) covers2 += x - span2->x;
                do
                {
                    cover = XorFormula::calculate(*covers1++, *covers2++);
                    if(cover) sl.add_cell(x, cover);
                    ++x;
                }
                while(--len);
                break;

            case 1:      // span1 is solid, span2 is AA
                covers2 = span2->covers;
                if(span2->x < x) covers2 += x - span2->x;
                do
                {
                    cover = XorFormula::calculate(*(span1->covers), *covers2++);
                    if(cover) sl.add_cell(x, cover);
                    ++x;
                }
                while(--len);
                break;

            case 2:      // span1 is AA, span2 is solid
                covers1 = span1->covers;
                if(span1->x < x) covers1 += x - span1->x;
                do
                {
                    cover = XorFormula::calculate(*covers1++, *(span2->covers));
                    if(cover) sl.add_cell(x, cover);
                    ++x;
                }
                while(--len);
                break;

            case 3:      // Both are solid spans
                cover = XorFormula::calculate(*(span1->covers), *(span2->covers));
                if(cover) sl.add_span(x, len, cover);
                break;

            }
        }
    };





    //-----------------------------------------------sbool_subtract_spans_aa
    // Functor.
    // Unite two spans preserving the anti-aliasing information.
    // The result is added to the "sl" scanline.
    //------------------
    template<class Scanline1, 
             class Scanline2, 
             class Scanline, 
             unsigned CoverShift = cover_shift> 
    struct sbool_subtract_spans_aa
    {
        enum cover_scale_e
        {
            cover_shift = CoverShift,
            cover_size  = 1 << cover_shift,
            cover_mask  = cover_size - 1,
            cover_full  = cover_mask
        };
        

        void operator () (const typename Scanline1::const_iterator& span1, 
                          const typename Scanline2::const_iterator& span2, 
                          int x, unsigned len, 
                          Scanline& sl) const
        {
            unsigned cover;
            const typename Scanline1::cover_type* covers1;
            const typename Scanline2::cover_type* covers2;

            // Calculate the operation code and choose the 
            // proper combination algorithm.
            // 0 = Both spans are of AA type
            // 1 = span1 is solid, span2 is AA
            // 2 = span1 is AA, span2 is solid
            // 3 = Both spans are of solid type
            //-----------------
            switch((span1->len < 0) | ((span2->len < 0) << 1))
            {
            case 0:      // Both are AA spans
                covers1 = span1->covers;
                covers2 = span2->covers;
                if(span1->x < x) covers1 += x - span1->x;
                if(span2->x < x) covers2 += x - span2->x;
                do
                {
                    cover = *covers1++ * (cover_mask - *covers2++);
                    if(cover)
                    {
                        sl.add_cell(x, 
                                    (cover == cover_full * cover_full) ?
                                    cover_full : 
                                    (cover >> cover_shift));
                    }
                    ++x;
                }
                while(--len);
                break;

            case 1:      // span1 is solid, span2 is AA
                covers2 = span2->covers;
                if(span2->x < x) covers2 += x - span2->x;
                do
                {
                    cover = *(span1->covers) * (cover_mask - *covers2++);
                    if(cover)
                    {
                        sl.add_cell(x, 
                                    (cover == cover_full * cover_full) ?
                                    cover_full : 
                                    (cover >> cover_shift));
                    }
                    ++x;
                }
                while(--len);
                break;

            case 2:      // span1 is AA, span2 is solid
                covers1 = span1->covers;
                if(span1->x < x) covers1 += x - span1->x;
                if(*(span2->covers) != cover_full)
                {
                    do
                    {
                        cover = *covers1++ * (cover_mask - *(span2->covers));
                        if(cover)
                        {
                            sl.add_cell(x, 
                                        (cover == cover_full * cover_full) ?
                                        cover_full : 
                                        (cover >> cover_shift));
                        }
                        ++x;
                    }
                    while(--len);
                }
                break;

            case 3:      // Both are solid spans
                cover = *(span1->covers) * (cover_mask - *(span2->covers));
                if(cover)
                {
                    sl.add_span(x, len, 
                                (cover == cover_full * cover_full) ?
                                cover_full : 
                                (cover >> cover_shift));
                }
                break;
            }
        }
    };






    //--------------------------------------------sbool_add_spans_and_render
    template<class Scanline1, 
             class Scanline, 
             class Renderer, 
             class AddSpanFunctor>
    void sbool_add_spans_and_render(const Scanline1& sl1, 
                                    Scanline& sl, 
                                    Renderer& ren, 
                                    AddSpanFunctor add_span)
    {
        sl.reset_spans();
        typename Scanline1::const_iterator span = sl1.begin();
        unsigned num_spans = sl1.num_spans();
        for(;;)
        {
            add_span(span, span->x, abs((int)span->len), sl);
            if(--num_spans == 0) break;
            ++span;
        }
        sl.finalize(sl1.y());
        ren.render(sl);
    }







    //---------------------------------------------sbool_intersect_scanlines
    // Intersect two scanlines, "sl1" and "sl2" and generate a new "sl" one.
    // The combine_spans functor can be of type sbool_combine_spans_bin or
    // sbool_intersect_spans_aa. First is a general functor to combine
    // two spans without Anti-Aliasing, the second preserves the AA
    // information, but works slower
    //
    template<class Scanline1, 
             class Scanline2, 
             class Scanline, 
             class CombineSpansFunctor>
    void sbool_intersect_scanlines(const Scanline1& sl1, 
                                   const Scanline2& sl2, 
                                   Scanline& sl, 
                                   CombineSpansFunctor combine_spans)
    {
        sl.reset_spans();

        unsigned num1 = sl1.num_spans();
        if(num1 == 0) return;

        unsigned num2 = sl2.num_spans();
        if(num2 == 0) return;

        typename Scanline1::const_iterator span1 = sl1.begin();
        typename Scanline2::const_iterator span2 = sl2.begin();

        while(num1 && num2)
        {
            int xb1 = span1->x;
            int xb2 = span2->x;
            int xe1 = xb1 + abs((int)span1->len) - 1;
            int xe2 = xb2 + abs((int)span2->len) - 1;

            // Determine what spans we should advance in the next step
            // The span with the least ending X should be advanced
            // advance_both is just an optimization when we ending 
            // coordinates are the same and we can advance both
            //--------------
            bool advance_span1 = xe1 <  xe2;
            bool advance_both  = xe1 == xe2;

            // Find the intersection of the spans
            // and check if they intersect
            //--------------
            if(xb1 < xb2) xb1 = xb2;
            if(xe1 > xe2) xe1 = xe2;
            if(xb1 <= xe1)
            {
                combine_spans(span1, span2, xb1, xe1 - xb1 + 1, sl);
            }

            // Advance the spans
            //--------------
            if(advance_both)
            {
                --num1;
                --num2;
                if(num1) ++span1;
                if(num2) ++span2;
            }
            else
            {
                if(advance_span1)
                {
                    --num1;
                    if(num1) ++span1;
                }
                else
                {
                    --num2;
                    if(num2) ++span2;
                }
            }
        }
    }








    //------------------------------------------------sbool_intersect_shapes
    // Intersect the scanline shapes. Here the "Scanline Generator" 
    // abstraction is used. ScanlineGen1 and ScanlineGen2 are 
    // the generators, and can be of type rasterizer_scanline_aa<>.
    // There function requires three scanline containers that can be of
    // different types.
    // "sl1" and "sl2" are used to retrieve scanlines from the generators,
    // "sl" is ised as the resulting scanline to render it.
    // The external "sl1" and "sl2" are used only for the sake of
    // optimization and reusing of the scanline objects.
    // the function calls sbool_intersect_scanlines with CombineSpansFunctor 
    // as the last argument. See sbool_intersect_scanlines for details.
    //----------
    template<class ScanlineGen1, 
             class ScanlineGen2, 
             class Scanline1, 
             class Scanline2, 
             class Scanline, 
             class Renderer,
             class CombineSpansFunctor>
    void sbool_intersect_shapes(ScanlineGen1& sg1, ScanlineGen2& sg2,
                                Scanline1& sl1, Scanline2& sl2,
                                Scanline& sl, Renderer& ren, 
                                CombineSpansFunctor combine_spans)
    {
        // Prepare the scanline generators.
        // If anyone of them doesn't contain 
        // any scanlines, then return.
        //-----------------
        if(!sg1.rewind_scanlines()) return;
        if(!sg2.rewind_scanlines()) return;

        // Get the bounding boxes
        //----------------
        rect_i r1(sg1.min_x(), sg1.min_y(), sg1.max_x(), sg1.max_y());
        rect_i r2(sg2.min_x(), sg2.min_y(), sg2.max_x(), sg2.max_y());

        // Calculate the intersection of the bounding 
        // boxes and return if they don't intersect.
        //-----------------
        rect_i ir = intersect_rectangles(r1, r2);
        if(!ir.is_valid()) return;

        // Reset the scanlines and get two first ones
        //-----------------
        sl.reset(ir.x1, ir.x2);
        sl1.reset(sg1.min_x(), sg1.max_x());
        sl2.reset(sg2.min_x(), sg2.max_x());
        if(!sg1.sweep_scanline(sl1)) return;
        if(!sg2.sweep_scanline(sl2)) return;