How to get a BufferedImage from a Component in java ?

Question

I know how to get a BufferedImage from JComponent, but how to get a BufferedImage from a Component in java ? The emphasis here is an object of the "Component" type rather than JComponent.

I tried the following method, but it return an all black image, what's wrong with it ?

  public static BufferedImage Get_Component_Image(Component myComponent,Rectangle region) throws IOException
  {
    BufferedImage img = new BufferedImage(myComponent.getWidth(), myComponent.getHeight(), BufferedImage.TYPE_INT_RGB);
    Graphics g = img.getGraphics();
    myComponent.paint(g);
    g.dispose();
    return img;
  }

Answer 1

You could try to use Component.paintAll.

You could also pass a reference to a Graphics object (coming from your buffered image) to SwingUtilities.paintComponent.

Answer 2

Component has a method paint(Graphics). That method will paint itself on the passed graphics. This is what we are going to use to create the BufferedImage, because BufferedImage has the handy method getGraphics(). That returns a Graphics-object which you can use to draw on the BufferedImage.

UPDATE: But we have to pre-configure the graphics for the paint method. That's what I found about the AWT Component rendering at java.sun.com:

When AWT invokes this method, the Graphics object parameter is pre-configured with the appropriate state for drawing on this particular component:

• The Graphics object's color is set to the component's foreground property.
• The Graphics object's font is set to the component's font property.
• The Graphics object's translation is set such that the coordinate (0,0) represents the upper left corner of the component.
• The Graphics object's clip rectangle is set to the area of the component that is in need of repainting.

So, this is our resulting method:

public static BufferedImage componentToImage(Component component, Rectangle region) throws IOException
{
    BufferedImage img = new BufferedImage(component.getWidth(), component.getHeight(), BufferedImage.TYPE_INT_ARGB_PRE);
    Graphics g = img.getGraphics();
    g.setColor(component.getForeground());
    g.setFont(component.getFont());
    component.paintAll(g);
    if (region == null)
    {
        region = new Rectangle(0, 0, img.getWidth(), img.getHeight());
    }
    return img.getSubimage(region.x, region.y, region.width, region.height);
}