static int drawThoughtLine_width = 10;

static void drawThoughtLine(BufferedImage bg,
  BufferedImage img1, int x1, int y1,
  BufferedImage img2, int x2, int y2, Color color) {
  Graphics2D g = imageGraphics(bg);
  g.setColor(color);
  g.setStroke(new BasicStroke(drawThoughtLine_width));
  g.drawLine(x1, y1, x2, y2);
  g.dispose();
}