    template<typename tc>
    CImg<T>& draw_line(int x0, int y0, const float z0,
                       int x1, int y1, const float z1,
                       const CImg<tc>& texture,
                       const int tx0, const int ty0,
                       const int tx1, const int ty1,
                       const float opacity=1,
                       const unsigned int pattern=~0U, const bool init_hatch=true) {
      if (is_empty() || z0<=0 || z1<=0 || !opacity || !pattern) return *this;
      if (texture._depth>1 || texture._spectrum<_spectrum)
        throw CImgArgumentException(_cimg_instance
                                    "draw_line(): Invalid specified texture (%u,%u,%u,%u,%p).",
                                    cimg_instance,
                                    texture._width,texture._height,texture._depth,texture._spectrum,texture._data);
      if (is_overlapped(texture))
        return draw_line(x0,y0,z0,x1,y1,z1,+texture,tx0,ty0,tx1,ty1,opacity,pattern,init_hatch);

      if (std::min(y0,y1)>=height() || std::max(y0,y1)<0 || std::min(x0,x1)>=width() || std::max(x0,x1)<0) return *this;

      float iz0 = 1/z0, iz1 = 1/z1;
      int
        w1 = width() - 1, h1 = height() - 1,
        dx01 = x1 - x0, dy01 = y1 - y0;
      float
        diz01 = iz1 - iz0,
        txz0 = tx0*iz0, txz1 = tx1*iz1,
        tyz0 = ty0*iz0, tyz1 = ty1*iz1,
        dtxz01 = txz1 - txz0, dtyz01 = tyz1 - tyz0;

      const bool is_horizontal = cimg::abs(dx01)>cimg::abs(dy01);
      if (is_horizontal) cimg::swap(x0,y0,x1,y1,w1,h1,dx01,dy01);
      if (pattern==~0U && y0>y1) {
        cimg::swap(x0,x1,y0,y1,iz0,iz1,txz0,txz1,tyz0,tyz1);
        dx01*=-1; dy01*=-1; diz01*=-1; dtxz01*=-1; dtyz01*=-1;
      }

      const ulongT twhd = (ulongT)texture._width*texture._height*texture._depth;
      static unsigned int hatch = ~0U - (~0U>>1);
      if (init_hatch) hatch = ~0U - (~0U>>1);
      cimg_init_scanline(opacity);

      const int
        step = y0<=y1?1:-1, hdy01 = dy01*cimg::sign(dx01)/2,
        cy0 = cimg::cut(y0,0,h1), cy1 = cimg::cut(y1,0,h1) + step;
      dy01+=dy01?0:1;

      for (int y = cy0; y!=cy1; y+=step) {
        const int
          yy0 = y - y0,
          x = x0 + (dx01*yy0 + hdy01)/dy01;
        const float
          iz = iz0 + diz01*yy0/dy01,
          txz = txz0 + dtxz01*yy0/dy01,
          tyz = tyz0 + dtyz01*yy0/dy01;
        if (x>=0 && x<=w1 && pattern&hatch) {
          const int
            tx = (int)cimg::round(txz/iz),
            ty = (int)cimg::round(tyz/iz);
          T *const ptrd = is_horizontal?data(y,x):data(x,y);
          const tc *const color = &texture._atXY(tx,ty);
          cimg_forC(*this,c) {
            const T val = color[c*twhd];
            ptrd[c*_sc_whd] = (T)(opacity>=1?val:val*_sc_nopacity + ptrd[c*_sc_whd]*_sc_copacity);
          }
        }
        if (!(hatch>>=1)) hatch = ~0U - (~0U>>1);
      }
      return *this;
Unknown