void render(mapnik::image_rgba8 const& image) const
    {
        agg::rendering_buffer buf(current_buffer_.bytes(), current_buffer_.width(),
                                  current_buffer_.height(), current_buffer_.row_size());
        ras_ptr_->reset();
        value_double gamma = get<value_double, keys::gamma>(sym_, feature_, common_.vars_);
        gamma_method_enum gamma_method = get<gamma_method_enum, keys::gamma_method>(sym_, feature_, common_.vars_);
        if (gamma != gamma_ || gamma_method != gamma_method_)
        {
            set_gamma_method(ras_ptr_, gamma, gamma_method);
            gamma_method_ = gamma_method;
            gamma_ = gamma;
        }

        using vertex_converter_type = vertex_converter<clip_poly_tag,
                                                       transform_tag,
                                                       affine_transform_tag,
                                                       simplify_tag,
                                                       smooth_tag>;
        using pattern_type = agg_polygon_pattern<vertex_converter_type>;

        pattern_type pattern(image, common_, sym_, feature_, prj_trans_);

        pattern_type::pixfmt_type pixf(buf);
        pixf.comp_op(static_cast<agg::comp_op_e>(get<composite_mode_e, keys::comp_op>(sym_, feature_, common_.vars_)));
        pattern_type::renderer_base renb(pixf);

        unsigned w = image.width();
        unsigned h = image.height();
        agg::rendering_buffer pattern_rbuf((agg::int8u*)image.bytes(),w,h,w*4);
        agg::pixfmt_rgba32_pre pixf_pattern(pattern_rbuf);
        pattern_type::img_source_type img_src(pixf_pattern);

        if (prj_trans_.equal() && pattern.clip_) pattern.converter_.set<clip_poly_tag>();

        ras_ptr_->filling_rule(agg::fill_even_odd);

        pattern.render(renb, *ras_ptr_);
    }
    void render(mapnik::image_rgba8 const& image) const
    {
        agg::rendering_buffer buf(current_buffer_.bytes(), current_buffer_.width(),
                                  current_buffer_.height(), current_buffer_.row_size());
        ras_ptr_->reset();
        value_double gamma = get<value_double, keys::gamma>(sym_, feature_, common_.vars_);
        gamma_method_enum gamma_method = get<gamma_method_enum, keys::gamma_method>(sym_, feature_, common_.vars_);
        if (gamma != gamma_ || gamma_method != gamma_method_)
        {
            set_gamma_method(ras_ptr_, gamma, gamma_method);
            gamma_method_ = gamma_method;
            gamma_ = gamma;
        }

        value_bool clip = get<value_bool, keys::clip>(sym_, feature_, common_.vars_);
        value_double opacity = get<double, keys::opacity>(sym_, feature_, common_.vars_);
        value_double simplify_tolerance = get<value_double, keys::simplify_tolerance>(sym_, feature_, common_.vars_);
        value_double smooth = get<value_double, keys::smooth>(sym_, feature_, common_.vars_);

        box2d<double> clip_box = clipping_extent(common_);

        using col = agg::rgba8;
        using order = agg::order_rgba;
        using blender_type = agg::comp_op_adaptor_rgba_pre<col, order>;
        using pixfmt_type = agg::pixfmt_custom_blend_rgba<blender_type, agg::rendering_buffer>;

        using wrap_x_type = agg::wrap_mode_repeat;
        using wrap_y_type = agg::wrap_mode_repeat;
        using img_source_type = agg::image_accessor_wrap<agg::pixfmt_rgba32_pre,
                                                         wrap_x_type,
                                                         wrap_y_type>;

        using span_gen_type = agg::span_pattern_rgba<img_source_type>;
        using ren_base = agg::renderer_base<pixfmt_type>;

        using renderer_type = agg::renderer_scanline_aa_alpha<ren_base,
                                                              agg::span_allocator<agg::rgba8>,
                                                              span_gen_type>;

        pixfmt_type pixf(buf);
        pixf.comp_op(static_cast<agg::comp_op_e>(get<composite_mode_e, keys::comp_op>(sym_, feature_, common_.vars_)));
        ren_base renb(pixf);

        unsigned w = image.width();
        unsigned h = image.height();
        agg::rendering_buffer pattern_rbuf((agg::int8u*)image.bytes(),w,h,w*4);
        agg::pixfmt_rgba32_pre pixf_pattern(pattern_rbuf);
        img_source_type img_src(pixf_pattern);

        pattern_alignment_enum alignment = get<pattern_alignment_enum, keys::alignment>(sym_, feature_, common_.vars_);
        unsigned offset_x=0;
        unsigned offset_y=0;

        if (alignment == LOCAL_ALIGNMENT)
        {
            double x0 = 0;
            double y0 = 0;
            using apply_local_alignment = detail::apply_local_alignment;
            apply_local_alignment apply(common_.t_,prj_trans_, clip_box, x0, y0);
            util::apply_visitor(geometry::vertex_processor<apply_local_alignment>(apply), feature_.get_geometry());

            offset_x = unsigned(current_buffer_.width() - x0);
            offset_y = unsigned(current_buffer_.height() - y0);
        }

        span_gen_type sg(img_src, offset_x, offset_y);

        agg::span_allocator<agg::rgba8> sa;
        renderer_type rp(renb,sa, sg, unsigned(opacity * 255));

        agg::trans_affine tr;
        auto transform = get_optional<transform_type>(sym_, keys::geometry_transform);
        if (transform) evaluate_transform(tr, feature_, common_.vars_, *transform, common_.scale_factor_);
        using vertex_converter_type = vertex_converter<clip_poly_tag,
                                                       transform_tag,
                                                       affine_transform_tag,
                                                       simplify_tag,
                                                       smooth_tag>;

        vertex_converter_type converter(clip_box, sym_,common_.t_,prj_trans_,tr,feature_,common_.vars_,common_.scale_factor_);

        if (prj_trans_.equal() && clip) converter.set<clip_poly_tag>();
        converter.set<transform_tag>(); //always transform
        converter.set<affine_transform_tag>(); // optional affine transform
        if (simplify_tolerance > 0.0) converter.set<simplify_tag>(); // optional simplify converter
        if (smooth > 0.0) converter.set<smooth_tag>(); // optional smooth converter

        using apply_vertex_converter_type = detail::apply_vertex_converter<vertex_converter_type, rasterizer>;
        using vertex_processor_type = geometry::vertex_processor<apply_vertex_converter_type>;
        apply_vertex_converter_type apply(converter, *ras_ptr_);
        mapnik::util::apply_visitor(vertex_processor_type(apply),feature_.get_geometry());
        agg::scanline_u8 sl;
        ras_ptr_->filling_rule(agg::fill_even_odd);
        agg::render_scanlines(*ras_ptr_, sl, rp);
    }