JScrollPane - 相对于鼠标位置进行缩放

Question

我需要在放大图像时计算视口的新位置.

UI构建如下:

• ImagePanel绘制图像
• ImagePanelWrapper是围绕imagePanel的JPanel
• JScrollPane包含ImagePanelWrapper

放大或缩小时,ImagePanel的缩放系数会发生变化,并且会重新计算ImagePanel的首选大小.因此,即使ImagePanel停留在相同的视口点,此面板上的图像也会移动.

当用户按住CTRL并使用鼠标滚轮时,将调用以下方法.给定的点是MouseWheelListener提供的光标位置.利用这些方法中的功能,当放大或缩小时,图像已经停留在相同的左上位置.

问题是我只是想弄清楚如何相对于鼠标移动,例如Paint.NET.有任何想法吗？

/**
 * 
 */
public void zoomOut(Point point) {
    this.imagePanel.setZoom(this.imagePanel.getZoom() * 0.9f);
    Point pos = this.getViewport().getViewPosition();

    int newX = (int) (pos.x * 0.9f);
    int newY = (int) (pos.y * 0.9f);
    this.getViewport().setViewPosition(new Point(newX, newY));

    this.imagePanel.revalidate();
    this.imagePanel.repaint();
}

/**
 * 
 */
public void zoomIn(Point point) {
    this.imagePanel.setZoom(this.imagePanel.getZoom() * 1.1f);
    Point pos = this.getViewport().getViewPosition();

    int newX = (int) (pos.x * 1.1f);
    int newY = (int) (pos.y * 1.1f);
    this.getViewport().setViewPosition(new Point(newX, newY));

    this.imagePanel.revalidate();
    this.imagePanel.repaint();
}

Answer 1

如果这些假设成立:

• 提供的Point相对于视口的左上角.
• 视口的尺寸小于底层的ImagePanel.

然后可以调整视口,以便在缩放操作之前和之后光标位于图像中的同一点上,如果按以下方式移动:

 /**
 * 
 */
public void zoomOut(Point point) {
    this.imagePanel.setZoom(this.imagePanel.getZoom() * 0.9f);
    Point pos = this.getViewport().getViewPosition();

    int newX = (int)(point.x*(0.9f - 1f) + 0.9f*pos.x);
    int newY = (int)(point.y*(0.9f - 1f) + 0.9f*pos.y);
    this.getViewport().setViewPosition(new Point(newX, newY));

    this.imagePanel.revalidate();
    this.imagePanel.repaint();
}

/**
 * 
 */
public void zoomIn(Point point) {
    this.imagePanel.setZoom(this.imagePanel.getZoom() * 1.1f);
    Point pos = this.getViewport().getViewPosition();

    int newX = (int)(point.x*(1.1f - 1f) + 1.1f*pos.x);
    int newY = (int)(point.y*(1.1f - 1f) + 1.1f*pos.y);
    this.getViewport().setViewPosition(new Point(newX, newY));

    this.imagePanel.revalidate();
    this.imagePanel.repaint();
}

这是完整性的数学: