Java2D，放大函数的图形

Question

我正在开发一个项目，我必须显示函数的图形并放大该图形。完全放大或简单地放大一个矩形，在该矩形中仅放大选定的部分。问题是，我不知道如何做到这一点，所以我请求您提供一些指导。

这是我的代码，我如何放大图形？

import java.awt.Color;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;

class SimpleJava2DExample extends Frame {
    private static final long serialVersionUID = 1L;
    double XRmin, XRmax, YRmin, YRmax;
    int XEmin, XEmax, YEmin, YEmax;
    double Sx, Sy;
    int Nsteps;
    String textMessage;
    double deltaY = 0.3;

    // Constructor
    SimpleJava2DExample() {
        textMessage = "";
        XEmin = YEmin = 10;
        Nsteps = 100;
        XRmin = -Math.PI / 2.;
        XRmax = 3 * Math.PI / 2.;// XRmax = 7*Math.PI;
        // Calculates YRmin, YRmax
        YRmin = F(XRmin);
        YRmax = F(XRmax);
        double xr, yr;
        for (int i = 0; i < Nsteps; i++) {
            xr = XRmin + (XRmax - XRmin) * i / Nsteps;
            yr = F(xr);
            if (yr < YRmin)
                YRmin = yr;
            if (yr > YRmax)
                YRmax = yr;
        }
        YRmax += deltaY;
        // Enables the closing of the window.
        WindowListener listener = new WindowAdapter() {
            // Override
            public void windowClosing(WindowEvent w) {
                System.exit(0);
            }
        };
        addWindowListener(listener);
        // Mouse click event
        MouseListener mouselistener = new MouseAdapter() {
            public void mouseClicked(MouseEvent e) {
                int ex = (int) e.getPoint().getX();
                int ey = (int) e.getPoint().getY();
                textMessage = "(x, y) : (" + Xreal(ex) + ", " + Yreal(ey) + ")";
                repaint();
            }
        };
        addMouseListener(mouselistener);
        // Enables the resize of the window.
        addComponentListener(new ComponentAdapter() {
            @Override
            public void componentResized(ComponentEvent arg0) {
                repaint();
            }
        });
    }

    // The function to be plotted
    double F(double x) {
        return (double) ((Math.sin(x) + 0.5 * Math.sin(3 * x)) * Math.exp(-1.0
                * x));
    }

    // Conversions between user (real) space and device space
    // Conversion Xreal --> Xdevice
    int Xpix(double xr) {
        return XEmin + (int) ((xr - XRmin) * Sx);
    }

    // Conversion Yreal --> Ydevice
    int Ypix(double yr) {
        return YEmax - (int) ((yr - YRmin) * Sy);
    }

    // Conversion Xdevice --> Xreal
    double Xreal(double xe) {
        return XRmin + (xe - XEmin) / Sx;
    }

    // Conversion Ydevice --> Yreal
    double Yreal(double ye) {
        return YRmin + (YEmax - ye) / Sy;
    }

    // This function plots the axes of the graph
    void drawAxes(Graphics2D g2d) {
        g2d.setColor(Color.black);
        g2d.drawLine(Xpix(XRmin), Ypix(0.0), Xpix(XRmax), Ypix(0.0));
        g2d.drawLine(Xpix(0.0), Ypix(YRmin), Xpix(0.0), Ypix(YRmax));
        int fontsize = this.getFont().getSize();
        g2d.drawString("0", Xpix(0.0) - fontsize, Ypix(0.0) + fontsize);
        g2d.drawString("" + XRmax, Xpix(XRmax) - 8 * fontsize, Ypix(0.0)
                - fontsize);
        g2d.drawString("" + XRmin, Xpix(XRmin), Ypix(0.0) - fontsize);
        g2d.drawString("" + YRmax, Xpix(0.0) + fontsize, Ypix(YRmax) + 4
                * fontsize);
        g2d.drawString("" + YRmin, Xpix(0.0) + fontsize, Ypix(YRmin) - fontsize);
    }

    public void paint(Graphics g) {
        super.paint(g);
        // In order to use Java 2D, it is necessary to cast the Graphics object
        // into a Graphics2D object.

        Graphics2D g2d = (Graphics2D) g;
        // The current size of the window
        XEmax = this.getWidth() - 50;
        YEmax = this.getHeight() - 50;
        // Calculates the scale factors
        Sx = (XEmax - XEmin) / (XRmax - XRmin);
        Sy = (YEmax - YEmin) / (YRmax - YRmin);
        // Draw the axes
        drawAxes(g2d);
        // Draw the graph
        g2d.setColor(Color.red);
        double xr, yr;
        Point2D lastPoint = new Point2D.Double(Xpix(XRmin), Ypix(YRmin));
        for (int i = 1; i < Nsteps; i++) {
            xr = XRmin + (XRmax - XRmin) * i / Nsteps;
            yr = F(xr);
            Point2D currentPoint = new Point2D.Double(Xpix(xr), Ypix(yr));
            g2d.draw(new Line2D.Double(lastPoint, currentPoint));
            lastPoint = currentPoint;
        }
        g2d.setColor(Color.blue);
        int fontsize = this.getFont().getSize();
        g2d.drawString(textMessage, 2 * fontsize, this.getHeight() - 2
                * fontsize);
        textMessage = "";
    }
}

public class MainJava2D {

    public static void main(String[] args) {
        //Generate the window.
        SimpleJava2DExample f = new SimpleJava2DExample();
        //Define a title for the window.
        String s = new String("The first Java 2D graph of a univariate function");
        f.setTitle(s);
        //Definition of the window size in pixels
        f.setSize(500, 400);
        //Show the window on the screen.
        f.setVisible(true);
    }
}

Answer 1

缩放所有内容的最简单方法是 scale Graphics2D 对象位于 Paint 方法的开头，但在此之前保存旧的 AffineTransform 并在最后重置它。

// save the original transform so that it can be restored later
AffineTransform oldTransform = g2d.getTransform();
g2d.scale(zoom, zoom);
...
// use g2d normally
...
// restore the transform because the same Graphics2D object
// might be used to draw other components
g2d.setTransform(oldTransform );

正如 Andrew Thompson 所评论的，您可能应该使用 Swing 而不是非常旧的 AWT - 如果您这样做，那么您需要重写 PaintComponent (而不是 Paint)，但缩放机制是相同的。