调整 JComponent 的大小以进行文件导出

Question

我有一个 JPanel，在上面使用通常的“paintComponent(Graphics g)”方法绘制了许多自定义编写的 JComponent。我使用 JLayeredPane 来控制自定义组件的显示顺序，如下所示：

public Class MyPanel extends JPanel {
    private JLayeredPane layeredPane = new JLayeredPane();
    private JComponent component1;
    private JComponent component2;

    public MyPanel() {
        super();
        setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));

        component1 = new CustomComponent1();
        layeredPane.add (component1, new Integer(0));

        component2 = new CustomComponent2();
        layeredPane.add (component2, new Integer(1));

        add (layeredPane);
    }

    public void resizePanel(Graphics g, int newWidth, int newHeight) {
        component1.setBounds (f(x), f(y), f(newWidth), f(newHeight));
        component2.setBounds (f(x), f(y), f(newWidth), f(newHeight));
    }

    public void paintComponent(Graphics g) {
        if ((getWidth() != oldWidth) || (getHeight() != oldHeight)) {
            oldWidth = getWidth();
            oldHeight = getHeight();
            resizePanel (g, getWidth(), getHeight());
        }
        super.paintComponent(g);
    }

现在，我想将此面板导出到 JPEG 文件，但具有不同的大小。当我使用以下代码时，它成功创建/导出所需大小的 JPEG 文件，但它还将面板的屏幕图像版本更新为新大小！哎呀！

public void export(File file, int width, int height)
    throws IOException
{
    BufferedImage scaledImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    Graphics2D g2 = scaledImage.createGraphics();
    resizePanel (g2, width, height);
    super.paintComponent (g2);

    try {
        OutputStream out = new FileOutputStream(file);
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
        encoder.encode(scaledImage);
        out.close();
    } catch (FileNotFoundException e) {
        throw new IOException ("Unable to export chart to ("
                  + file.getAbsolutePath() + "): " + e.getLocalizedMessage());
    } finally {
        g2.dispose();
    }
}

如何“绘制”适合导出的图像，但实际上不会显示该新图像？

谢谢！

---

好吧，我又回到这个问题了......

我正在绘制的场景包含一些文本，现在最终用户希望以“肖像”长宽比导出图形。由于我不是在新的维度中重新绘制场景，而只是缩放图像，这会导致文本在水平方向上被严重挤压。

无论如何？

Answer 1

看起来是第二个优秀的解决方案。我的最终解决方案如下所示：

public void export(File file, int width, int height)
throws IOException
{
    BufferedImage scaledImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    Graphics2D g2 = scaledImage.createGraphics();
    g2.scale(((double) width)/((double)getWidth()), ((double) height)/((double)getHeight()));
    paintComponents(g2);
    try {
        ImageIO.write(scaledImage, "jpg", file);            
    } catch (FileNotFoundException e) {
        throw new IOException ("Unable to export chart to ("
         + file.getAbsolutePath() + "): " + e.getLocalizedMessage());
    } finally {
        g2.dispose();
    }
}

Answer 2

根本不要调整面板的大小；只需创建一个 BufferedImage 这是面板的当前大小并绘制它。获得快照后，立即将其缩放到所需的尺寸 BufferedImage 使用 drawImage () 或 AffineTransformOp。

附录： AffineTransformOp< 的一个优点/code>是对旋转、插值、缩放和纵横比的控制：

BufferedImage image = ...
int w = image.getWidth();
int h = image.getHeight();
AffineTransform scaleTransform = new AffineTransform();
// last-in-first-applied: rotate, scale
scaleTransform.scale(scaleX, scaleY);
scaleTransform.rotate(Math.PI / 2, w / 2, h / 2);
AffineTransformOp scaleOp = new AffineTransformOp(
        scaleTransform, AffineTransformOp.TYPE_BILINEAR);
BufferedImage new = scaleOp.filter(image, null);

Answer 3

好吧，让一切看起来都正常的唯一方法（例如，在光栅化后不缩放文本）是使用新尺寸在新图形上下文上绘制图像。这是我的新“export()”方法。

    public void export(File file, final int width, final int height)
    throws IOException
{

    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    final Graphics2D g2 = image.createGraphics();

    //  Must wait for the bloody image to be drawn as Swing 'paint()' methods
    //  merely schedule painting events.  The 'draw()' below may not complete
    //  the painting process before the 'write()' of the image is performed.

    //  thus, we wait....

    try {
        SwingUtilities.invokeAndWait(new Runnable() {
            public void run() {
                draw (g2, new Rectangle (0, 0, width, height));
            }
        });
        ImageIO.write(image, "png", file);
    } catch (Exception e) {
        throw new IOException ("Unable to export chart to ("
                + file.getAbsolutePath() + "): " + e.getLocalizedMessage());
    } finally {
        g2.dispose();
    }
}

上面调用的“draw()”方法在我的所有子组件上调用“setbounds()”方法，将它们绘制到新的缓冲图像上。有点工作，但结果正是我需要的。