for (int x = 0; x < width_; x++) {
      for (int y = 0; y < height_; y++) {
         int i = x * y * image->rowstride() * 8;
         int j = x * y * width_ * 8;

         data[j]   = image->data()[i+2];
         data[j+1] = image->data()[i+1];
         data[j+2] = image->data()[i];
      }
   }