agg_span_image_filter_rgb.h

这是VCF框架的代码

//----------------------------------------------------------------------------
// 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: [e-mail]
//          [e-mail]
//          http://www.antigrain.com
//----------------------------------------------------------------------------
//
// Adaptation for high precision colors has been sponsored by 
// Liberty Technology Systems, Inc., visit http://lib-sys.com
//
// Liberty Technology Systems, Inc. is the provider of
// PostScript and PDF technology for software developers.
// 
//----------------------------------------------------------------------------
#ifndef AGG_SPAN_IMAGE_FILTER_RGB_INCLUDED
#define AGG_SPAN_IMAGE_FILTER_RGB_INCLUDED

#include "agg_basics.h"
#include "agg_color_rgba.h"
#include "agg_span_image_filter.h"


namespace agg
{

    //===============================================span_image_filter_rgb_nn
    template<class Source, class Interpolator> 
    class span_image_filter_rgb_nn : 
    public span_image_filter<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_filter<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::calc_type calc_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask
        };

        //--------------------------------------------------------------------
        span_image_filter_rgb_nn() {}
        span_image_filter_rgb_nn(source_type& src, 
                                 interpolator_type& inter) :
            base_type(src, inter, 0) 
        {}

        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);
            do
            {
                base_type::interpolator().coordinates(&x, &y);
                const value_type* fg_ptr = (const value_type*)
                    base_type::source().span(x >> image_subpixel_shift, 
                                             y >> image_subpixel_shift, 
                                             1);
                span->r = fg_ptr[order_type::R];
                span->g = fg_ptr[order_type::G];
                span->b = fg_ptr[order_type::B];
                span->a = base_mask;
                ++span;
                ++base_type::interpolator();

            } while(--len);
        }
    };



    //==========================================span_image_filter_rgb_bilinear
    template<class Source, class Interpolator> 
    class span_image_filter_rgb_bilinear : 
    public span_image_filter<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_filter<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::calc_type calc_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask
        };

        //--------------------------------------------------------------------
        span_image_filter_rgb_bilinear() {}
        span_image_filter_rgb_bilinear(source_type& src, 
                                       interpolator_type& inter) :
            base_type(src, inter, 0) 
        {}


        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);
            calc_type fg[3];
            const value_type *fg_ptr;
            do
            {
                int x_hr;
                int y_hr;

                base_type::interpolator().coordinates(&x_hr, &y_hr);

                x_hr -= base_type::filter_dx_int();
                y_hr -= base_type::filter_dy_int();

                int x_lr = x_hr >> image_subpixel_shift;
                int y_lr = y_hr >> image_subpixel_shift;

                unsigned weight;

                fg[0] = 
                fg[1] = 
                fg[2] = image_subpixel_scale * image_subpixel_scale / 2;

                x_hr &= image_subpixel_mask;
                y_hr &= image_subpixel_mask;

                fg_ptr = (const value_type*)base_type::source().span(x_lr, y_lr, 2);
                weight = (image_subpixel_scale - x_hr) * 
                         (image_subpixel_scale - y_hr);
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg_ptr = (const value_type*)base_type::source().next_x();
                weight = x_hr * (image_subpixel_scale - y_hr);
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg_ptr = (const value_type*)base_type::source().next_y();
                weight = (image_subpixel_scale - x_hr) * y_hr;
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg_ptr = (const value_type*)base_type::source().next_x();
                weight = x_hr * y_hr;
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                span->r = value_type(fg[order_type::R] >> (image_subpixel_shift * 2));
                span->g = value_type(fg[order_type::G] >> (image_subpixel_shift * 2));
                span->b = value_type(fg[order_type::B] >> (image_subpixel_shift * 2));
                span->a = base_mask;

                ++span;
                ++base_type::interpolator();

            } while(--len);
        }
    };



    //=====================================span_image_filter_rgb_bilinear_clip
    template<class Source, class Interpolator> 
    class span_image_filter_rgb_bilinear_clip : 
    public span_image_filter<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_filter<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::calc_type calc_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask
        };

        //--------------------------------------------------------------------
        span_image_filter_rgb_bilinear_clip() {}
        span_image_filter_rgb_bilinear_clip(source_type& src, 
                                            const color_type& back_color,
                                            interpolator_type& inter) :
            base_type(src, inter, 0),
            m_back_color(back_color)
        {}
        const color_type& background_color() const { return m_back_color; }
        void background_color(const color_type& v)   { m_back_color = v; }

        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);
            calc_type fg[3];
            calc_type src_alpha;
            value_type back_r = m_back_color.r;
            value_type back_g = m_back_color.g;
            value_type back_b = m_back_color.b;
            value_type back_a = m_back_color.a;

            const value_type *fg_ptr;

            int maxx = base_type::source().width() - 1;
            int maxy = base_type::source().height() - 1;

            do
            {
                int x_hr;
                int y_hr;
                
                base_type::interpolator().coordinates(&x_hr, &y_hr);

                x_hr -= base_type::filter_dx_int();
                y_hr -= base_type::filter_dy_int();

                int x_lr = x_hr >> image_subpixel_shift;
                int y_lr = y_hr >> image_subpixel_shift;
                unsigned weight;

                if(x_lr >= 0    && y_lr >= 0 &&
                   x_lr <  maxx && y_lr <  maxy) 
                {
                    fg[0] = 
                    fg[1] = 
                    fg[2] = image_subpixel_scale * image_subpixel_scale / 2;

                    x_hr &= image_subpixel_mask;
                    y_hr &= image_subpixel_mask;

                    fg_ptr = (const value_type*)
                        base_type::source().row_ptr(y_lr) + x_lr + x_lr + x_lr;

                    weight = (image_subpixel_scale - x_hr) * 
                             (image_subpixel_scale - y_hr);
                    fg[0] += weight * *fg_ptr++;
                    fg[1] += weight * *fg_ptr++;
                    fg[2] += weight * *fg_ptr++;

                    weight = x_hr * (image_subpixel_scale - y_hr);
                    fg[0] += weight * *fg_ptr++;
                    fg[1] += weight * *fg_ptr++;
                    fg[2] += weight * *fg_ptr++;

                    ++y_lr;
                    fg_ptr = (const value_type*)
                        base_type::source().row_ptr(y_lr) + x_lr + x_lr + x_lr;

                    weight = (image_subpixel_scale - x_hr) * y_hr;
                    fg[0] += weight * *fg_ptr++;
                    fg[1] += weight * *fg_ptr++;
                    fg[2] += weight * *fg_ptr++;

                    weight = x_hr * y_hr;
                    fg[0] += weight * *fg_ptr++;
                    fg[1] += weight * *fg_ptr++;
                    fg[2] += weight * *fg_ptr++;

                    fg[0] >>= image_subpixel_shift * 2;
                    fg[1] >>= image_subpixel_shift * 2;
                    fg[2] >>= image_subpixel_shift * 2;
                    src_alpha = base_mask;
                }
                else
                {
                    if(x_lr < -1   || y_lr < -1 ||
                       x_lr > maxx || y_lr > maxy)
                    {
                        fg[order_type::R] = back_r;
                        fg[order_type::G] = back_g;
                        fg[order_type::B] = back_b;
                        src_alpha         = back_a;
                    }
                    else
                    {
                        fg[0] = 
                        fg[1] = 
                        fg[2] = 
                        src_alpha = image_subpixel_scale * image_subpixel_scale / 2;

                        x_hr &= image_subpixel_mask;
                        y_hr &= image_subpixel_mask;

                        weight = (image_subpixel_scale - x_hr) * 
                                 (image_subpixel_scale - y_hr);
                        if(x_lr >= 0    && y_lr >= 0 &&