void render_marker(agg::trans_affine const& marker_tr, double opacity)
 {
     render_raster_marker(RendererType(renb_), ras_, this->src_, this->feature_, marker_tr, opacity);
     if (!placed_)
     {
         pixmap_.add_feature(this->feature_);
         placed_ = true;
     }
 }
 void render_marker(agg::trans_affine const& marker_tr, double opacity)
 {
     // In the long term this should be a visitor pattern based on the type of render this->src_ provided that converts
     // the destination pixel type required.
     render_raster_marker(RendererType(renb_), ras_, this->src_, this->feature_, marker_tr, opacity);
     if (!placed_)
     {
         pixmap_.add_feature(this->feature_);
         placed_ = true;
     }
 }