1    /* 
2     * A program to paint, centered on the canvas, a circle of randomly colored, unframed dots 
3     * that are separated. 
4     * */
5    
6            package npw;
7    
8    import painter.SPainter;
9    import shapes.SCircle;
10   
11   import javax.swing.*;
12   import java.awt.*;
13   import java.util.Random;
14   import java.util.Scanner;
15   
16   public class HirstDots {
17   
18       private void paintTheImage() {
19           // Get the input information
20           int radius = getNumber("circle radius");
21           int dotRadius = getNumber("dot radius");
22   
23           // Establish the painter
24           SPainter painter = new SPainter("Hirst Dots", radius * 2 + 50, radius * 2 + 50);
25           painter.setBrushWidth(3);
26           SCircle circle = new SCircle(radius);
27           SCircle dot = new SCircle(dotRadius);
28   
29           // Paint the dots
30           paintHirstDots(painter, circle, dot);
31       }
32   
33       private void paintHirstDots(SPainter painter, SCircle circle, SCircle dot) {
34           // Position the painter to begin drawing the rows
35           painter.mfd(circle.radius());
36           painter.tr();
37           // Paint the circle of squares
38           double moved = 0;
39           while (moved < circle.diameter()) {
40               double chord = chordLength(circle.radius() - moved, circle);
41               int dots = dotsOnLineCount(chord, dot.diameter());
42               paintRow(painter, dot, dots);
43               nextRow(painter, dot.diameter());
44               moved = moved + dot.diameter();
45           }
46           // Make the method invariant with respect to painter position
47           painter.tl();
48           painter.mfd(circle.radius());
49       }
50   
51       // Move to the next row
52       private void nextRow(SPainter painter, double rowHeight) {
53           painter.tr();
54           painter.mfd(rowHeight);
55           painter.tl();
56       }
57   
58       // Assumes the painter is at the center of the row to paint, facing right.
59       private void paintRow(SPainter painter, SCircle dot, int dotsToPaint) {
60           // Move backward 1/2 of the length we're painting to get ready to paint the row.
61           double centerOffset = ((dotsToPaint * dot.diameter()) / 2) - dot.diameter() / 2;
62           painter.mbk(centerOffset);
63   
64           // Paint the row of squares.
65           int painted = 0;
66           while (painted < dotsToPaint) {
67               paintOneDot(painter, dot);
68               painter.mfd(dot.diameter());
69               painted = painted + 1;
70           }
71   
72           // Make the method invariant with respect to painter position.
73           painter.mbk(centerOffset + dot.diameter());
74       }
75   
76       private void paintOneDot(SPainter painter, SCircle dot) {
77           dot.s2();
78           painter.setColor(randomColor());
79           painter.paint(dot);
80           dot.x2();
81       }
82   
83       private static int dotsOnLineCount(double lineLength, double diameterLength) {
84           int dots = ((int) Math.ceil((lineLength - diameterLength) / diameterLength) + 1);
85           return dots;
86       }
87   
88       private double chordLength(double yOffset, SCircle circle) {
89           double xLength = Math.sqrt(Math.pow(circle.radius(), 2) - Math.pow(yOffset, 2));
90           double chordLength = xLength * 2;
91           return chordLength;
92       }
93   
94       private static int getNumber(String prompt) {
95           String nss = JOptionPane.showInputDialog(null, prompt + "?");
96           Scanner scanner = new Scanner(nss);
97           return scanner.nextInt();
98       }
99   
100      private static Color randomColor() {
101          Random rgen = new Random();
102          int r = rgen.nextInt(256);
103          int g = rgen.nextInt(256);
104          int b = rgen.nextInt(256);
105          return new Color(r, g, b);
106      }
107  
108      public HirstDots() {
109          paintTheImage();
110      }
111  
112      public static void main(String[] args) {
113          SwingUtilities.invokeLater(new Runnable() {
114              public void run() {
115                  new HirstDots();
116              }
117          });
118      }
119  }
120