[Java画图]画函数图像

利用Graphics类画任意显式函数图像，只需修改代码中的F()函数即可，另外调整timesx和timesy参数来分方向放大或缩小图像。需要重定义坐标系。

 package test;

 import javax.swing.*;
 import java.awt.Graphics;

 public class DrawFunction extends JFrame {
     static double timesx = 10, timesy = 10;
     double F(double x) {
         return Math.sin(x) / Math.pow(1.1, -x);//函数表达式
     }
     int x0, y0;
     static int W = 800, H = 600;
     static double L = -W / 2, R = W / 2;
     Graphics G;
     public void setOrigin(int x, int y) {
         this.x0 = x;
         this.y0 = y;
         // show coordinate axis
         drawLine(-W / 2, 0, W / 2, 0);
         drawLine(0, -H / 2, 0, H / 2);
         drawString("X", W / 2 - 30, -20);
         drawString("Y", -20, H / 2 - 20);
         for (int i = 1; i <= 10; i ++) {
             draw(W / 2 - i - 6, i);
             draw(W / 2 - i - 6, -i);
         }
         for (int i = 1; i <= 10; i ++) {
             draw(-i, H / 2 - i);
             draw(i, H / 2 - i);
         }
     }
     public DrawFunction() {
         add(new NewPanel());
     }
     public static void main(String[] args) {
         DrawFunction frame = new DrawFunction();
         frame.setTitle("DrawFunction");
         frame.setSize(W, H);
         frame.setLocationRelativeTo(null);
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setVisible(true);
         frame.setResizable(false);
     }
     public class Coordinate2D {
         int x, y;
         public Coordinate2D(int x, int y) {
             this.x = x;
             this.y = y;
         }
         public int getPixelPointX() {
             return x0 + x;
         }
         public int getPixelPointY() {
             return y0 - y;
         }
     }
     class NewPanel extends JPanel {
         protected void paintComponent(Graphics g) {
             super.paintComponent(g);
             G = g;
             setOrigin(W / 2, H / 2);
             // in the following , draw what you want draw!
             for (int i = -W / 2; i <= W / 2; i ++) {
                 draw(i, work(i));
             }
             /*
             for (int i = 0; i < 1000; i ++) {
                 int x = (int)(Math.random() * 400 - 200);
                 int y = (int)(Math.random() * 400 - 200);
                 drawString("哈哈", x, y);
             }
             */
         }
     }
     int work(int x) {
         //timesx = 0.01;
         //timesy = 100;
         return (int)(F(x / timesx) * timesy);
     }
     public void draw(int x, int y) {
         int X = new Coordinate2D(x, y).getPixelPointX();
         int Y = new Coordinate2D(x, y).getPixelPointY();
         G.drawLine(X, Y, X, Y);
     }
     public void drawRec(int x1, int y1, int x2, int y2) {
         int dx = x1 < x2? 1 : -1;
         int dy = y1 < y2? 1 : -1;
         for (int i = x1; i != x2 + dx; i += dx) {
             for (int j = y1; j != y2 + dy; j += dy) {
                 draw(i, j);
             }
         }
     }
     public void drawLine(int x1, int y1, int x2, int y2) {
         int dx = x1 < x2? 1 : -1;
         if (x1 == x2) drawRec(x1, y1, x2, y2);
         else {
             double d = (double)(y2 - y1) / (x2 - x1);
             for (int i = x1; i != x2 + dx; i += dx) {
                 draw(i, (int)(y1 + (i - x1) * d));
             }
         }
     }
     public void drawString(String s, int x, int y) {
         int X = new Coordinate2D(x, y).getPixelPointX();
         int Y = new Coordinate2D(x, y).getPixelPointY();
         G.drawString(s, X, Y);
     }
 }