static BWImage bwImage_markColumnsWhite(int w, int h, L<? extends Number> columns) {
  BWImage img = new(w, h, 0f);
  for (Number i : columns) {
    int col = iround(i);
    if (col >= 0 && col < w)
      for y to h: img.setPixel(col, y, 1f);
  }
  ret img;
}