244 lines
8.1 KiB
C
244 lines
8.1 KiB
C
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//----------------------------------------------------------------------------
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// Anti-Grain Geometry - Version 2.4
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// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
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//
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// Permission to copy, use, modify, sell and distribute this software
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// is granted provided this copyright notice appears in all copies.
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// This software is provided "as is" without express or implied
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// warranty, and with no claim as to its suitability for any purpose.
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//
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//----------------------------------------------------------------------------
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// Contact: mcseem@antigrain.com
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// mcseemagg@yahoo.com
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// http://www.antigrain.com
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//----------------------------------------------------------------------------
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//
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// Adaptation for high precision colors has been sponsored by
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// Liberty Technology Systems, Inc., visit http://lib-sys.com
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//
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// Liberty Technology Systems, Inc. is the provider of
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// PostScript and PDF technology for software developers.
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//
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//----------------------------------------------------------------------------
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#ifndef AGG_SPAN_GOURAUD_GRAY_INCLUDED
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#define AGG_SPAN_GOURAUD_GRAY_INCLUDED
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#include <cmath>
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#include <cstdlib>
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#include "agg_basics.h"
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#include "agg_color_gray.h"
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#include "agg_dda_line.h"
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#include "agg_span_gouraud.h"
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namespace agg
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{
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//=======================================================span_gouraud_gray
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template<class ColorT> class span_gouraud_gray : public span_gouraud<ColorT>
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{
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public:
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typedef ColorT color_type;
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typedef typename color_type::value_type value_type;
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typedef span_gouraud<color_type> base_type;
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typedef typename base_type::coord_type coord_type;
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enum subpixel_scale_e
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{
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subpixel_shift = 4,
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subpixel_scale = 1 << subpixel_shift
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};
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private:
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//--------------------------------------------------------------------
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struct gray_calc
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{
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void init(const coord_type& c1, const coord_type& c2)
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{
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m_x1 = c1.x - 0.5;
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m_y1 = c1.y - 0.5;
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m_dx = c2.x - c1.x;
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double dy = c2.y - c1.y;
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m_1dy = (std::fabs(dy) < 1e-10) ? 1e10 : 1.0 / dy;
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m_v1 = c1.color.v;
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m_a1 = c1.color.a;
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m_dv = c2.color.v - m_v1;
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m_da = c2.color.a - m_a1;
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}
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void calc(double y)
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{
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double k = (y - m_y1) * m_1dy;
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if(k < 0.0) k = 0.0;
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if(k > 1.0) k = 1.0;
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m_v = m_v1 + iround(m_dv * k);
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m_a = m_a1 + iround(m_da * k);
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m_x = iround((m_x1 + m_dx * k) * subpixel_scale);
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}
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double m_x1;
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double m_y1;
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double m_dx;
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double m_1dy;
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int m_v1;
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int m_a1;
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int m_dv;
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int m_da;
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int m_v;
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int m_a;
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int m_x;
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};
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public:
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//--------------------------------------------------------------------
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span_gouraud_gray() {}
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span_gouraud_gray(const color_type& c1,
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const color_type& c2,
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const color_type& c3,
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double x1, double y1,
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double x2, double y2,
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double x3, double y3,
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double d = 0) :
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base_type(c1, c2, c3, x1, y1, x2, y2, x3, y3, d)
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{}
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//--------------------------------------------------------------------
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void prepare()
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{
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coord_type coord[3];
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base_type::arrange_vertices(coord);
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m_y2 = int(coord[1].y);
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m_swap = cross_product(coord[0].x, coord[0].y,
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coord[2].x, coord[2].y,
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coord[1].x, coord[1].y) < 0.0;
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m_c1.init(coord[0], coord[2]);
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m_c2.init(coord[0], coord[1]);
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m_c3.init(coord[1], coord[2]);
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}
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//--------------------------------------------------------------------
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void generate(color_type* span, int x, int y, unsigned len)
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{
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m_c1.calc(y);
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const gray_calc* pc1 = &m_c1;
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const gray_calc* pc2 = &m_c2;
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if(y < m_y2)
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{
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// Bottom part of the triangle (first subtriangle)
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//-------------------------
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m_c2.calc(y + m_c2.m_1dy);
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}
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else
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{
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// Upper part (second subtriangle)
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//-------------------------
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m_c3.calc(y - m_c3.m_1dy);
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pc2 = &m_c3;
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}
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if(m_swap)
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{
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// It means that the triangle is oriented clockwise,
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// so that we need to swap the controlling structures
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//-------------------------
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const gray_calc* t = pc2;
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pc2 = pc1;
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pc1 = t;
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}
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// Get the horizontal length with subpixel accuracy
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// and protect it from division by zero
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//-------------------------
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int nlen = std::abs(pc2->m_x - pc1->m_x);
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if(nlen <= 0) nlen = 1;
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dda_line_interpolator<14> v(pc1->m_v, pc2->m_v, nlen);
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dda_line_interpolator<14> a(pc1->m_a, pc2->m_a, nlen);
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// Calculate the starting point of the gradient with subpixel
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// accuracy and correct (roll back) the interpolators.
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// This operation will also clip the beginning of the span
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// if necessary.
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//-------------------------
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int start = pc1->m_x - (x << subpixel_shift);
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v -= start;
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a -= start;
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nlen += start;
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int vv, va;
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enum lim_e { lim = color_type::base_mask };
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// Beginning part of the span. Since we rolled back the
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// interpolators, the color values may have overflow.
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// So that, we render the beginning part with checking
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// for overflow. It lasts until "start" is positive;
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// typically it's 1-2 pixels, but may be more in some cases.
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//-------------------------
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while(len && start > 0)
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{
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vv = v.y();
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va = a.y();
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if(vv < 0) vv = 0; if(vv > lim) vv = lim;
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if(va < 0) va = 0; if(va > lim) va = lim;
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span->v = (value_type)vv;
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span->a = (value_type)va;
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v += subpixel_scale;
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a += subpixel_scale;
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nlen -= subpixel_scale;
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start -= subpixel_scale;
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++span;
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--len;
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}
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// Middle part, no checking for overflow.
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// Actual spans can be longer than the calculated length
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// because of anti-aliasing, thus, the interpolators can
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// overflow. But while "nlen" is positive we are safe.
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//-------------------------
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while(len && nlen > 0)
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{
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span->v = (value_type)v.y();
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span->a = (value_type)a.y();
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v += subpixel_scale;
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a += subpixel_scale;
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nlen -= subpixel_scale;
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++span;
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--len;
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}
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// Ending part; checking for overflow.
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// Typically it's 1-2 pixels, but may be more in some cases.
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//-------------------------
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while(len)
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{
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vv = v.y();
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va = a.y();
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if(vv < 0) vv = 0; if(vv > lim) vv = lim;
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if(va < 0) va = 0; if(va > lim) va = lim;
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span->v = (value_type)vv;
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span->a = (value_type)va;
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v += subpixel_scale;
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a += subpixel_scale;
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++span;
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--len;
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}
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}
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private:
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bool m_swap;
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int m_y2;
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gray_calc m_c1;
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gray_calc m_c2;
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gray_calc m_c3;
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};
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}
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#endif
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