Add java

src/Spirograph.java

@@ -0,0 +1,129 @@
+import javax.swing.*;
+import java.awt.*;
+import java.awt.geom.Line2D;
+import java.awt.image.BufferedImage;
+import java.util.Timer;
+import java.util.TimerTask;
+
+public class Spirograph extends JPanel {
+
+	// drawing parameters
+	private double X1, Y1, R1, S1, Q1, L1;
+	private double X2, Y2, R2, S2, Q2, L2;
+	private double S3, Q3;
+
+	// positions of pen and arm joints
+	private double x = Double.NaN, y;
+	private double p1x, p1y;
+	private double p2x, p2y;
+
+	private BufferedImage img;
+	private Graphics2D g;
+
+	private Spirograph() {
+
+		// disc 1: position, radius, rot. speed & offset, arm length
+		X1 = 250;
+		Y1 = 100;
+		R1 = 50;
+		S1 = .16;
+		Q1 = 0;
+		L1 = 200;
+
+		// disc 2
+		X2 = 550;
+		Y2 = 100;
+		R2 = 50;
+		S2 = .166;
+		Q2 = 0;
+		L2 = 200;
+
+		// rotation of canvas
+		S3 = 0.001;
+		Q3 = 0;
+
+		init();
+	}
+
+	public static void main(String[] args) {
+		Spirograph circles = new Spirograph();
+
+		JFrame frame = new JFrame();
+		frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
+		frame.setResizable(false);
+		frame.add(circles);
+		frame.pack();
+		frame.setLocationRelativeTo(null);
+		frame.setVisible(true);
+
+		circles.run();
+	}
+
+	private void init() {
+		Dimension dim = new Dimension(900, 900);
+		setPreferredSize(dim);
+		img = new BufferedImage(dim.width, dim.height, BufferedImage.TYPE_INT_RGB);
+		g = img.createGraphics();
+		g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
+		g.rotate(Q3, img.getWidth() / 2.0, img.getHeight() / 2.0);
+	}
+
+	private void run() {
+		new Timer().scheduleAtFixedRate(new TimerTask() {
+			@Override
+			public void run() {
+
+				// arm joint positions
+				p1x = X1 + R1 * Math.cos(Q1);
+				p1y = Y1 + R1 * Math.sin(Q1);
+				p2x = X2 + R2 * Math.cos(Q2);
+				p2y = Y2 + R2 * Math.sin(Q2);
+
+				double d = (p1x - p2x) * (p1x - p2x) + (p1y - p2y) * (p1y - p2y);
+				double ld1 = L1 * L1 / d, ld2 = L2 * L2 / d;
+				double l = (ld1 - ld2 + 1) / 2;
+				double h = Math.sqrt(ld1 - l * l);
+
+				double prevX = x, prevY = y;
+				x = l * (p2x - p1x) - h * (p2y - p1y) + p1x;
+				y = l * (p2y - p1y) + h * (p2x - p1x) + p1y;
+
+				g.setColor(Color.getHSBColor((float) (Q3 / (2 * Math.PI)), 1, 1));
+				// prevX is NaN only on the very first frame to avoid drawing a line from the origin
+				if (!Double.isNaN(prevX)) g.draw(new Line2D.Double(prevX, prevY, x, y));
+
+				g.rotate(S3, img.getWidth() / 2.0, img.getHeight() / 2.0);
+
+				Q1 += S1;
+				Q2 += S2;
+				Q3 += S3;
+				repaint();
+			}
+		}, 0, 8);
+	}
+
+	@Override
+	public void paintComponent(Graphics graphics) {
+		super.paintComponent(graphics);
+		Graphics2D g = (Graphics2D) graphics;
+		g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
+
+		// draw canvas
+		g.drawImage(img, 0, 0, null);
+
+		// draw overlay
+		// 1. canvas rotation
+		g.rotate(Q3, img.getWidth() / 2.0, img.getHeight() / 2.0);
+
+		// 2. disc 1
+		g.setColor(Color.GREEN);
+		g.drawOval((int) (X1 - R1), (int) (Y1 - R1), (int) (2 * R1), (int) (2 * R1));
+		g.drawLine((int) (p1x), (int) (p1y), (int) (x), (int) (y));
+
+		// 3. disc 2
+		g.setColor(Color.ORANGE);
+		g.drawOval((int) (X2 - R2), (int) (Y2 - R2), (int) (2 * R2), (int) (2 * R2));
+		g.drawLine((int) (p2x), (int) (p2y), (int) (x), (int) (y));
+	}
+
+}