CImg<T>& draw_triangle(int x0, int y0,
                           int x1, int y1,
                           int x2, int y2,
                           const tc *const color,
                           const CImg<tl>& light,
                           int lx0, int ly0,
                           int lx1, int ly1,
                           int lx2, int ly2,
                           const float opacity=1) {
      if (is_empty()) return *this;
      if (!color)
        throw CImgArgumentException(_cimg_instance
                                    "draw_triangle(): Specified color is (null).",
                                    cimg_instance);
      if (light._depth>1 || light._spectrum<_spectrum)
        throw CImgArgumentException(_cimg_instance
                                    "draw_triangle(): Invalid specified light texture (%u,%u,%u,%u,%p).",
                                    cimg_instance,light._width,light._height,light._depth,light._spectrum,light._data);

      if (y0>y1) cimg::swap(x0,x1,y0,y1,lx0,lx1,ly0,ly1);
      if (y0>y2) cimg::swap(x0,x2,y0,y2,lx0,lx2,ly0,ly2);
      if (y1>y2) cimg::swap(x1,x2,y1,y2,lx1,lx2,ly1,ly2);
      if (y2<0 || y0>=height() || cimg::min(x0,x1,x2)>=width() || cimg::max(x0,x1,x2)<0 || !opacity) return *this;

      const int
        w1 = width() - 1, h1 = height() - 1,
        dx01 = x1 - x0, dx02 = x2 - x0, dx12 = x2 - x1,
        dy01 = std::max(1,y1 - y0), dy02 = std::max(1,y2 - y0), dy12 = std::max(1,y2 - y1),
        cy0 = cimg::cut(y0,0,h1), cy2 = cimg::cut(y2,0,h1),
        hdy01 = dy01*cimg::sign(dx01)/2, hdy02 = dy02*cimg::sign(dx02)/2, hdy12 = dy12*cimg::sign(dx12)/2,
        dlx01 = lx1 - lx0, dlx02 = lx2 - lx0, dlx12 = lx2 - lx1,
        dly01 = ly1 - ly0, dly02 = ly2 - ly0, dly12 = ly2 - ly1,
        hdy01lx = dy01*cimg::sign(dlx01)/2, hdy02lx = dy02*cimg::sign(dlx02)/2, hdy12lx = dy12*cimg::sign(dlx12)/2,
        hdy01ly = dy01*cimg::sign(dly01)/2, hdy02ly = dy02*cimg::sign(dly02)/2, hdy12ly = dy12*cimg::sign(dly12)/2;

      const ulongT lwhd = (ulongT)light._width*light._height*light._depth;
      cimg_init_scanline(opacity);

      for (int y = cy0; y<=cy2; ++y) {
        const int yy0 = y - y0, yy1 = y - y1;
        int
          xm = y<y1?x0 + (dx01*yy0 + hdy01)/dy01:x1 + (dx12*yy1 + hdy12)/dy12,
          xM = x0 + (dx02*yy0 + hdy02)/dy02,
          lxm = y<y1?lx0 + (dlx01*yy0 + hdy01lx)/dy01:lx1 + (dlx12*yy1 + hdy12lx)/dy12,
          lxM = lx0 + (dlx02*yy0 + hdy02lx)/dy02,
          lym = y<y1?ly0 + (dly01*yy0 + hdy01ly)/dy01:ly1 + (dly12*yy1 + hdy12ly)/dy12,
          lyM = ly0 + (dly02*yy0 + hdy02ly)/dy02;
        if (xm>xM) cimg::swap(xm,xM,lxm,lxM,lym,lyM);
        if (xM>=0 && xm<=w1) {
          const int
            cxm = cimg::cut(xm,0,w1),
            cxM = cimg::cut(xM,0,w1);
          T *ptrd = data(cxm,y);
          const int
            dxmM = std::max(1,xM - xm), hdxmM = dxmM/2,
            dlxmM = lxM - lxm, dlymM = lyM - lym;

          for (int x = cxm; x<=cxM; ++x) {
            const int
              xxm = x - xm,
              lx = (lxm*dxmM + dlxmM*xxm + hdxmM)/dxmM,
              ly = (lym*dxmM + dlymM*xxm + hdxmM)/dxmM;
            const tl *const lig = &light._atXY(lx,ly);
            cimg_forC(*this,c) {
              const tc col = color[c];
              const float cbs = cimg::cut((float)lig[c*lwhd],0,2);
              const Tfloat val = cbs<=1?cbs*col:(2 - cbs)*col + (cbs - 1)*_sc_maxval;
              ptrd[c*_sc_whd] = (T)(opacity>=1?val:val*_sc_nopacity + ptrd[c*_sc_whd]*_sc_copacity);
            }
            ++ptrd;
          }
        }
      }
      return *this;
    }