AffineTransform：从其中心缩放一个Shape [英] AffineTransform: scaling a Shape from its center

问题描述

我试图使用AffineTransform从其中心缩放一个矩形。我确信解决方案很明显，但我无法完成它！这是我迄今为止测试过的内容...

I'm trying to scale a rectangle from its center using AffineTransform. I'm sure the solution is obvious but I cannot make it work ! Here is what I've tested so far...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.AffineTransform;

import javax.swing.JOptionPane;
import javax.swing.JPanel;

public class Test extends JPanel {
    Test()
        {
        super(null);
        setOpaque(true);
        setBackground(Color.WHITE);
        setPreferredSize(new Dimension(200,200));
        }
    @Override
    protected void paintComponent(Graphics g1) {
        super.paintComponent(g1);
        Rectangle r= new Rectangle(5,5,getWidth()-10,getHeight()-10);
        double cx= r.getCenterX();
        double cy= r.getCenterY();
        Graphics2D g=(Graphics2D)g1;
        g.setColor(Color.BLACK);
        AffineTransform old= g.getTransform();
        for(double zoom=0.9; zoom>=0.5; zoom-=0.1)
            {
            AffineTransform tr2= new AffineTransform(old);
            tr2.translate(-cx, -cy);
            tr2.scale(zoom, zoom);
            tr2.translate(cx/zoom,cy/zoom);
            g.setTransform(tr2);
            g.draw(r);
            g.setTransform(old);
            }
        }


    public static void main(String[] args) {
        JOptionPane.showMessageDialog(null, new Test());
        }
    }

但它不起作用....任何建议？

But it doesn't work.... Any suggestion ?

推荐答案

我明白你在处理矩形时的意思。原因是翻译的初始计算没有考虑到容器对象的大小。

I see what you mean when you're dealing with rectangles. The reason is because the initial calculation for the translation didn't take into account the size of the container object.

使用这个代替：

tr2.translate(
    (this.getWidth()/2) - (r.getWidth()*(zoom))/2,
    (this.getHeight()/2) - (r.getHeight()*(zoom))/2
);
tr2.scale(zoom,zoom);
g.setTransform(tr2);

在缩放之前，将矩形转换为面板的中心。在我的测试中，它工作得很好。

What this is doing is translating the rectangle to the center of the panel before scaling it. In my tests it works just fine.

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