如何使用另一个象限作为坐标在 JPanel 上绘图？

发布于 2024-08-27 14:22:22 字数 1244 浏览 12 评论 0原文

我想通过重写 paintComponent 在 JPanel 上绘制一些形状。我希望能够平移和缩放。使用 AffineTransform 和 Graphics2D 对象上的 setTransform 方法可以轻松实现平移和缩放。完成此操作后，我可以使用 g2.draw(myShape) 轻松绘制形状。形状是使用“世界坐标”定义的，因此平移时效果很好，我必须将它们转换到画布/JPanel绘制前的坐标。

现在我想更改坐标的象限。从JPanel和计算机经常使用的第四象限到用户最熟悉的第一象限。 X 轴相同，但 Y 轴应向上而不是向下增加。通过 new Point(origo.x, -origo.y); 重新定义 origo 很容易；

但是我怎样才能绘制这个象限中的形状？我想保留形状的坐标（在世界坐标中定义）而不是在画布坐标中。因此，我需要以某种方式转换它们，或者转换 Graphics2D 对象，并且我希望高效地做到这一点。我也可以使用 AffineTransform 来做到这一点吗？

我的绘图代码：

        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D)g;
            g2.setColor(Color.blue);

            AffineTransform at = g2.getTransform();
            at.translate(-origo.x, -origo.y);
            at.translate(0, getHeight());
            at.scale(1, -1);
            g2.setTransform(at);
            g2.drawLine(30, 30, 140, 20);
            g2.draw(new CubicCurve2D.Double(30, 65, 23, 45, 23, 34, 67, 58));
        }

原文

I would like to draw some shapes on a JPanel by overriding paintComponent. I would like to be able to pan and zoom. Panning and zooming is easy to do with AffineTransform and the setTransform method on the Graphics2D object. After doing that I can easyli draw the shapes with g2.draw(myShape) The shapes are defined with the "world coordinates" so it works fine when panning and I have to translate them to the canvas/JPanel coordinates before drawing.

Now I would like to change the quadrant of the coordinates. From the 4th quadrant that JPanel and computer often uses to the 1st quadrant that the users are most familiar with. The X is the same but the Y-axe should increase upwards instead of downwards. It is easy to redefine origo by new Point(origo.x, -origo.y);

But How can I draw the shapes in this quadrant? I would like to keep the coordinates of the shapes (defined in the world coordinates) rather than have them in the canvas coordinates. So I need to transform them in some way, or transform the Graphics2D object, and I would like to do it efficiently. Can I do this with AffineTransform too?

My code for drawing:

        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D)g;
            g2.setColor(Color.blue);

            AffineTransform at = g2.getTransform();
            at.translate(-origo.x, -origo.y);
            at.translate(0, getHeight());
            at.scale(1, -1);
            g2.setTransform(at);
            g2.drawLine(30, 30, 140, 20);
            g2.draw(new CubicCurve2D.Double(30, 65, 23, 45, 23, 34, 67, 58));
        }

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