如何从Java中的组件获取BufferedImage？ [英] How to get a BufferedImage from a Component in java?

问题描述

我知道如何从JComponent获取BufferedImage，但是如何从Java中的Component获取BufferedImage呢？

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.

我尝试了以下方法，但是它返回了全黑图像，这有什么问题呢？

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;
  }

推荐答案

组件具有方法 paint（Graphics）。该方法将自己绘制在传递的图形上。这就是我们用来创建 BufferedImage 的方法，因为BufferedImage具有方便的方法 getGraphics（）。这将返回一个 Graphics 对象，您可以使用该对象在 BufferedImage 上进行绘制。

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.

更新：但是我们必须为paint方法预先配置图形。这就是我在 java.sun.com ：

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:

当AWT调用此方法时，
Graphics对象参数为
并预先配置了适当的$用于绘制此特定
组件的b $ b状态：

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

• Graphics对象的颜色设置为组件的前台属性。 / li>
  
• 图形对象的字体设置为组件的font属性。


• 图形对象的转换设置为使得坐标（0,0）表示


• 将Graphics对象的剪辑矩形设置为需要重绘的组件区域。

因此，这是我们得到的方法：

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);
}

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