Question

我有一个正在绘制的JPanel，我正试图通过修改变量比例来使用鼠标滚轮“缩放”进出。现在发生的事情是你可以放大或缩小，但放大后向右和向下移动，然后在缩小时向后和向左移动。

我想这样做，以便它调整就好像你放大了JPanel中心的点，但我无法弄清楚如何计算正确的偏移量来翻译...

任何人都知道如何做到这一点，或者更好的是更清晰地实现整个平移和缩放能力？

我基本上是在绘制一系列坐标，这些坐标来自一个系统，其中0,0位于左下角，位于界限之间：

xMin = 661208
xMax = 662618

yMin = 4291657
yMax = 4293285

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    Graphics2D g2 = (Graphics2D) g;

    double scale = details.getScale();
    double xOffset = details.getxOffset();
    double yOffset = details.getyOffset();

    g2.scale(scale, -scale);

    // Dividing offset by scale makes panning 1:1 with the cursor still. yMax to account for the
    // fact we needed to flip around the y axis to make it right-side up.
    g2.translate((-xMin + xOffset / scale), (-yMax + yOffset / scale));

    // Code to draw stuff goes here.  It uses coordinates between xMin-xMax and yMin-yMax to draw.
    .
    .
    .
}

Answer 1

这是车轮的一个例子：

 public class GraphicsOnly extends JPanel implements MouseWheelListener {
      Shape[] shapes;
      Dimension size;
      double scale = 1.0;
      private static int source = 100;
      public GraphicsOnly() {
        addMouseWheelListener(this);
        size = new Dimension(10,10);
        setBackground(new Color(240,200,200));
    }



    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        if(shapes == null) initShapes();
        // Keep shapes centered on panel.
        double x = (getWidth()  - scale*size.width)/2;
        double y = (getHeight() - scale*size.height)/2;
        AffineTransform at = AffineTransform.getTranslateInstance(x, y);
        at.scale(scale, scale);
        g2.setPaint(Color.blue);
        g2.draw(at.createTransformedShape(shapes[0]));
        g2.setPaint(Color.green.darker());
        g2.draw(at.createTransformedShape(shapes[1]));
        g2.setPaint(new Color(240,240,200));
        g2.fill(at.createTransformedShape(shapes[2]));
        g2.setPaint(Color.red);
        g2.draw(at.createTransformedShape(shapes[2]));
    }

    public Dimension getPreferredSize() {
        int w = (int)(scale*size.width);
        int h = (int)(scale*size.height);
        return new Dimension(w, h);
    }

    private void initShapes() {
        shapes = new Shape[3];
        int w = getWidth();
        int h = getHeight();
        shapes[0] = new Rectangle2D.Double(w/16, h/16, w*7/8, h*7/8);
        shapes[1] = new Line2D.Double(w/16, h*15/16, w*15/16, h/16);
        shapes[2] = new Ellipse2D.Double(w/4, h/4, w/2, h/2);
        size.width = w;
        size.height = h;
    }


    public static void main(String[] args) {
        GraphicsOnly app = new GraphicsOnly();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new JScrollPane(app));
        f.setSize(400, 400);
        f.setLocation(200,200);
        f.setVisible(true);
    }

    @Override
    public void mouseWheelMoved(MouseWheelEvent e) {
        // TODO Auto-generated method stub
        if(e.getWheelRotation() >0){
            source = source-e.getScrollAmount();
        }else{
            source = source+e.getScrollAmount();
        }
        scale = source/100.0;
        System.out.println(scale);
        repaint();
        revalidate();
    }
}

Java Graphics2D平移和缩放/翻译和缩放

1 个答案: