英文:
Java Graphics2D - Zoom on mouse location
问题
我有一个绘制在上面的 JPanel。我想能够使用鼠标滚轮进行缩放，但我希望缩放到鼠标的位置，以使鼠标下的点保持不变。我在这里的 stackoverflow 上找到了一些问题，但它们对我没有起作用。
我通过实现这里描述的内容 2 几乎实现了我想要的效果。这是我的代码：
public class MyPanel extends JPanel {
...
private double zoom = 1;
private double zoom_old = 1;
private int zoomPointX;
private int zoomPointY;
...
class CustomMouseWheelListener implements MouseWheelListener {
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
zoomPointX = e.getX();
zoomPointY = e.getY();
if (e.getPreciseWheelRotation() < 0) {
zoom -= 0.1;
} else {
zoom += 0.1;
}
if (zoom < 0.01) {
zoom = 0.01;
}
repaint();
}
}
...
protected void paintComponent(Graphics g) {
Graphics2D g2D = (Graphics2D) g;
super.paintComponent(g2D);
if (zoom != zoom_old) {
double scalechange = zoom - zoom_old;
zoom_old = zoom;
double offsetX = -(zoomPointX * scalechange);
double offsetY = -(zoomPointY * scalechange) ;
AffineTransform at = new AffineTransform();
at.scale(zoom, zoom);
at.translate(offsetX, offsetY);
g2D.setTransform(at);
}
a_different_class_where_i_do_some_drawing.draw(g2D);
}
}
这几乎实现了我想要的效果。如果我尝试缩放，我注意到鼠标的位置被考虑在内，所以例如如果我将鼠标放在面板的左侧，它会在左侧大致缩放。然而，它并没有精确地缩放到鼠标，所以鼠标下的点仍然会改变。
有人能帮我修复这个问题吗？
编辑：
这里是上面发布的代码发生的情况的图片：我开始时鼠标在蓝色的方块上，然后只需用鼠标滚轮滚动。正如你所看到的，鼠标位置正在被改变：
英文:
I have a jpanel that I draw on. I would like to be able to zoom in and out using the mousewheel, but I want to zoom to the location of the mouse, such that the point under the mouse stays the same. I have found some questions here on stackoverflow, but they did not work for me.
I got pretty close to doing what I want by implementing what is described here. Here is my code:
public class MyPanel extends JPanel {
...
private double zoom = 1;
private double zoom_old = 1;
private int zoomPointX;
private int zoomPointY;
...
class CustomMouseWheelListener implements MouseWheelListener {
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
zoomPointX = e.getX();
zoomPointY = e.getY();
if (e.getPreciseWheelRotation() < 0) {
zoom -= 0.1;
} else {
zoom += 0.1;
}
if (zoom < 0.01) {
zoom = 0.01;
}
repaint();
}
}
...
protected void paintComponent(Graphics g) {
Graphics2D g2D = (Graphics2D) g;
super.paintComponent(g2D);
if (zoom != zoom_old) {
double scalechange = zoom - zoom_old;
zoom_old = zoom;
double offsetX = -(zoomPointX * scalechange);
double offsetY = -(zoomPointY * scalechange) ;
AffineTransform at = new AffineTransform();
at.scale(zoom, zoom);
at.translate(offsetX, offsetY);
g2D.setTransform(at);
}
a_different_class_where_i_do_some_drawing.draw(g2D);
}
}
This ALMOST does what I want. If I try to zoom, I notice that the position of the mouse is taken into account, so for example If I have my mouse on the left of the panel it will roughly zoom in on the left. However, it does not zoom exactly onto the mouse, so the point under the mouse still changes.
Can anyone help me fix this?
EDIT:
Here is a picture of what is happening with the code posted above: I start out with the mouse on the blue square and then just scroll with the mouse wheel. As you can see, the mouse position if being changed:
答案1
得分: 3
我通过实现这里所描述的内容来解决了这个问题。
以下是更新后的代码：
public class MyPanel extends JPanel {
...
private double zoom = 1;
private int zoomPointX;
private int zoomPointY;
...
class CustomMouseWheelListener implements MouseWheelListener {
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
zoomPointX = e.getX();
zoomPointY = e.getY();
if (e.getPreciseWheelRotation() < 0) {
zoom -= 0.1;
} else {
zoom += 0.1;
}
if (zoom < 0.01) {
zoom = 0.01;
}
repaint();
}
}
...
protected void paintComponent(Graphics g) {
Graphics2D g2D = (Graphics2D) g;
super.paintComponent(g2D);
AffineTransform at = g2D.getTransform();
at.translate(zoomPointX, zoomPointY);
at.scale(zoom, zoom);
at.translate(-zoomPointX, -zoomPointY);
g2D.setTransform(at);
a_different_class_where_i_do_some_drawing.draw(g2D);
}
}
英文:
I solved the problem by implementing what is being described here
Here is the updated code:
public class MyPanel extends JPanel {
...
private double zoom = 1;
private int zoomPointX;
private int zoomPointY;
...
class CustomMouseWheelListener implements MouseWheelListener {
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
zoomPointX = e.getX();
zoomPointY = e.getY();
if (e.getPreciseWheelRotation() < 0) {
zoom -= 0.1;
} else {
zoom += 0.1;
}
if (zoom < 0.01) {
zoom = 0.01;
}
repaint();
}
}
...
protected void paintComponent(Graphics g) {
Graphics2D g2D = (Graphics2D) g;
super.paintComponent(g2D);
AffineTransform at = g2D.getTransform();
at.translate(zoomPointX, zoomPointY);
at.scale(zoom, zoom);
at.translate(-zoomPointX, -zoomPointY);
g2D.setTransform(at);
a_different_class_where_i_do_some_drawing.draw(g2D);
}
}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论