//---------------------------------------------------------------------------- // Anti-Grain Geometry (AGG) - Version 2.5 // A high quality rendering engine for C++ // Copyright (C) 2002-2006 Maxim Shemanarev // Contact: mcseem@antigrain.com // mcseemagg@yahoo.com // http://antigrain.com // // AGG is free software; you can redistribute it and/or // modify it under the terms of the GNU General Public License // as published by the Free Software Foundation; either version 2 // of the License, or (at your option) any later version. // // AGG is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // You should have received a copy of the GNU General Public License // along with AGG; if not, write to the Free Software // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, // MA 02110-1301, USA. //---------------------------------------------------------------------------- // // 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_GOURAUD_GRAY_INCLUDED #define AGG_SPAN_GOURAUD_GRAY_INCLUDED #include "agg_basics.h" #include "agg_color_gray.h" #include "agg_dda_line.h" #include "agg_span_gouraud.h" namespace agg { //=======================================================span_gouraud_gray template<class ColorT> class span_gouraud_gray : public span_gouraud<ColorT> { public: typedef ColorT color_type; typedef typename color_type::value_type value_type; typedef span_gouraud<color_type> base_type; typedef typename base_type::coord_type coord_type; enum subpixel_scale_e { subpixel_shift = 4, subpixel_scale = 1 << subpixel_shift }; private: //-------------------------------------------------------------------- struct gray_calc { void init(const coord_type& c1, const coord_type& c2) { m_x1 = c1.x - 0.5; m_y1 = c1.y - 0.5; m_dx = c2.x - c1.x; double dy = c2.y - c1.y; m_1dy = (fabs(dy) < 1e-10) ? 1e10 : 1.0 / dy; m_v1 = c1.color.v; m_a1 = c1.color.a; m_dv = c2.color.v - m_v1; m_da = c2.color.a - m_a1; } void calc(double y) { double k = (y - m_y1) * m_1dy; if(k < 0.0) k = 0.0; if(k > 1.0) k = 1.0; m_v = m_v1 + iround(m_dv * k); m_a = m_a1 + iround(m_da * k); m_x = iround((m_x1 + m_dx * k) * subpixel_scale); } double m_x1; double m_y1; double m_dx; double m_1dy; int m_v1; int m_a1; int m_dv; int m_da; int m_v; int m_a; int m_x; }; public: //-------------------------------------------------------------------- span_gouraud_gray() {} span_gouraud_gray(const color_type& c1, const color_type& c2, const color_type& c3, double x1, double y1, double x2, double y2, double x3, double y3, double d = 0) : base_type(c1, c2, c3, x1, y1, x2, y2, x3, y3, d) {} //-------------------------------------------------------------------- void prepare() { coord_type coord[3]; base_type::arrange_vertices(coord); m_y2 = int(coord[1].y); m_swap = cross_product(coord[0].x, coord[0].y, coord[2].x, coord[2].y, coord[1].x, coord[1].y) < 0.0; m_c1.init(coord[0], coord[2]); m_c2.init(coord[0], coord[1]); m_c3.init(coord[1], coord[2]); } //-------------------------------------------------------------------- void generate(color_type* span, int x, int y, unsigned len) { m_c1.calc(y); const gray_calc* pc1 = &m_c1; const gray_calc* pc2 = &m_c2; if(y < m_y2) { // Bottom part of the triangle (first subtriangle) //------------------------- m_c2.calc(y + m_c2.m_1dy); } else { // Upper part (second subtriangle) //------------------------- m_c3.calc(y - m_c3.m_1dy); pc2 = &m_c3; } if(m_swap) { // It means that the triangle is oriented clockwise, // so that we need to swap the controlling structures //------------------------- const gray_calc* t = pc2; pc2 = pc1; pc1 = t; } // Get the horizontal length with subpixel accuracy // and protect it from division by zero //------------------------- int nlen = abs(pc2->m_x - pc1->m_x); if(nlen <= 0) nlen = 1; dda_line_interpolator<14> v(pc1->m_v, pc2->m_v, nlen); dda_line_interpolator<14> a(pc1->m_a, pc2->m_a, nlen); // Calculate the starting point of the gradient with subpixel // accuracy and correct (roll back) the interpolators. // This operation will also clip the beginning of the span // if necessary. //------------------------- int start = pc1->m_x - (x << subpixel_shift); v -= start; a -= start; nlen += start; int vv, va; enum lim_e { lim = color_type::base_mask }; // Beginning part of the span. Since we rolled back the // interpolators, the color values may have overflow. // So that, we render the beginning part with checking // for overflow. It lasts until "start" is positive; // typically it's 1-2 pixels, but may be more in some cases. //------------------------- while(len && start > 0) { vv = v.y(); va = a.y(); if(vv < 0) vv = 0; if(vv > lim) vv = lim; if(va < 0) va = 0; if(va > lim) va = lim; span->v = (value_type)vv; span->a = (value_type)va; v += subpixel_scale; a += subpixel_scale; nlen -= subpixel_scale; start -= subpixel_scale; ++span; --len; } // Middle part, no checking for overflow. // Actual spans can be longer than the calculated length // because of anti-aliasing, thus, the interpolators can // overflow. But while "nlen" is positive we are safe. //------------------------- while(len && nlen > 0) { span->v = (value_type)v.y(); span->a = (value_type)a.y(); v += subpixel_scale; a += subpixel_scale; nlen -= subpixel_scale; ++span; --len; } // Ending part; checking for overflow. // Typically it's 1-2 pixels, but may be more in some cases. //------------------------- while(len) { vv = v.y(); va = a.y(); if(vv < 0) vv = 0; if(vv > lim) vv = lim; if(va < 0) va = 0; if(va > lim) va = lim; span->v = (value_type)vv; span->a = (value_type)va; v += subpixel_scale; a += subpixel_scale; ++span; --len; } } private: bool m_swap; int m_y2; gray_calc m_c1; gray_calc m_c2; gray_calc m_c3; }; } #endif |