Method contour_create

dep/agg/include/agg_span_gradient_contour.h:194–396

DT algorithm by: Pedro Felzenszwalb

    // DT algorithm by: Pedro Felzenszwalb
    int8u* gradient_contour::contour_create(path_storage* ps)
    {
        int8u* result = NULL;

        if (ps)
        {
            // I. Render Black And White NonAA Stroke of the Path
            // Path Bounding Box + Some Frame Space Around [configurable]
            agg::conv_curve<agg::path_storage> conv(*ps);

            double x1, y1, x2, y2;

            if (agg::bounding_rect_single(conv, 0, &x1, &y1, &x2, &y2))
            {
                // Create BW Rendering Surface
                int width = int(ceil(x2 - x1)) + m_frame * 2 + 1;
                int height = int(ceil(y2 - y1)) + m_frame * 2 + 1;

                int8u* buffer = new int8u[width * height];

                if (buffer)
                {
                    std::memset(buffer, 255, width * height);

                    // Setup VG Engine & Render
                    agg::rendering_buffer rb;
                    rb.attach(buffer, width, height, width);

                    agg::pixfmt_gray8 pf(rb);
                    agg::renderer_base<agg::pixfmt_gray8> renb(pf);

                    agg::renderer_primitives<
                        agg::renderer_base<agg::pixfmt_gray8>>
                        prim(renb);
                    agg::rasterizer_outline<renderer_primitives<
                        agg::renderer_base<agg::pixfmt_gray8>>>
                        ras(prim);

                    agg::trans_affine mtx;
                    mtx *= agg::trans_affine_translation(
                        -x1 + m_frame, -y1 + m_frame);

                    agg::conv_transform<agg::conv_curve<agg::path_storage>>
                        trans(conv, mtx);

                    prim.line_color(agg::rgba8(0, 0, 0, 255));
                    ras.add_path(trans);

                    // II. Distance Transform
                    // Create Float Buffer + 0 vs infinity assignment
                    float* image = new float[width * height];

                    if (image)
                    {
                        for (int y = 0, l = 0; y < height; y++)
                        {
                            for (int x = 0; x < width; x++, l++)
                            {