如何从 JFrame 屏幕截图中删除标题栏?

I'm capturing a screenshot image of a JFrame via a "double buffering" approach, per below:

public BufferedImage getScreenshot() {      
  java.awt.Dimension dim = this.getPreferredSize();         
  BufferedImage image = new BufferedImage(dim.width, dim.height, BufferedImage.TYPE_INT_RGB);            
  this.paint(image.getGraphics());      
  return image;     
}

this 扩展了 JFrame.我得到的图像在标题栏所在的顶部有一个空白条.在不为标题栏分配额外空间的情况下捕获 JFrame 内容图像的最直接方法是什么?