Java Graphics2D 平移和缩放

Question

我有问题。我希望能够使用鼠标滚轮放大我的 Graphics2D 屏幕，但我也希望能够平移 Graphics2D 以便它位于我缩放的位置。这是到目前为止发生的事情：“http://cdn.makeagif.com/media/6-11-2015/E0kYGY.gif”它正确地转换为玩家的位置，但我希望它可以随着鼠标滚轮的滚动而放大和缩小。这是我到目前为止要做的代码：

private AffineTransform getCamTransform()
{
    AffineTransform t = new AffineTransform();
    float a = 400 - player.getX();
    float b = 250 - player.getY();
    t.translate(a, b);
    /*
     * Here's where I want to scale using the zoom
     * variable and also translate the g2d according
     * to the zoom variable.
     */
    return t;
}

private double zoom = 2.0D;

@Override
public void mouseWheelMoved(MouseWheelEvent e)
{
    zoom += e.getPreciseWheelRotation();
}

这只是我拥有的一小部分代码。我有一种方法可以将所有内容绘制到屏幕上，但这只是 return 必须应用于相机的变换。然后将变换设置为 Graphics2D.

的前一个变换

如果有更简单的方法或者我做错了，请告诉我。我也希望在 CPU 上也能有效率。感谢回答者！

Answer 1

基本思路是，您想让它看起来好像图形在可视区域内保持居中。我首先想到尝试缩放翻译点，也许这可能会起作用，但我无法让它起作用（3 岁想看书没有给我太多时间来试验）。

基本上，您需要添加另一个平移，根据可视区域和缩放将 x/y 点移动适当的量，使图像在可视区域内看起来保持静止，然后应用缩放以及其上的正常翻译...

        double width = getWidth();
        double height = getHeight();

        double zoomWidth = width * zoom;
        double zoomHeight = height * zoom;

        double anchorx = (width - zoomWidth) / 2;
        double anchory = (height - zoomHeight) / 2;

        AffineTransform at = new AffineTransform();
        at.translate(anchorx, anchory);
        at.scale(zoom, zoom);
        at.translate(-100, -100);

因此，anchorx/y 表示根据可视区域的宽度和高度，生成的图形需要偏移的量，以便图像将保留在其中 "centred"。 .

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseWheelEvent;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.text.NumberFormat;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private double zoom = 1d;
        private BufferedImage img;

        public TestPane() {
            try {
                img = ImageIO.read(new File("..."));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
            addMouseWheelListener(new MouseAdapter() {
                @Override
                public void mouseWheelMoved(MouseWheelEvent e) {
                    if (e.getPreciseWheelRotation() < 0) {
                        zoom -= 0.1;
                    } else {
                        zoom += 0.1;
                    }
//                  zoom += e.getPreciseWheelRotation();
                    if (zoom < 0.01) {
                        zoom = 0.01;
                    }

                    repaint();

                }
            });
        }

        public String format(double value) {
            return NumberFormat.getNumberInstance().format(value);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();

            double width = getWidth();
            double height = getHeight();

            double zoomWidth = width * zoom;
            double zoomHeight = height * zoom;

            double anchorx = (width - zoomWidth) / 2;
            double anchory = (height - zoomHeight) / 2;

            AffineTransform at = new AffineTransform();
            at.translate(anchorx, anchory);
            at.scale(zoom, zoom);
            at.translate(-100, -100);

            g2d.setTransform(at);
            g2d.drawImage(img, 0, 0, this);

            g2d.dispose();
        }

    }

}

可能有一个非常棒的数学公式，您可以用它来代替，但我是笨蛋 ;)

Java Graphics2D 平移和缩放

Java Graphics2D Translate and Scale

java

graphics2d