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