teaching machines

CS 245 Lecture 7 – Abstract Classes

February 11, 2014 by Chris Johnson. Filed under cs245, lectures, spring 2014.

Agenda

• what ?s
• the inheritance spectrum
• a transformation hierarchy

TODO

• Start homework 1. Due before February 24.

Code

Transform.java

package lecture07;

import java.awt.Point;

public abstract class Transform {
  protected double[][] matrix;
  
  public Transform() {
    matrix = new double[3][3];
  }
  
  public Point apply(Point in) {
    int newX = (int) (matrix[0][0] * in.x + matrix[0][1] * in.y + matrix[0][2]);
    int newY = (int) (matrix[1][0] * in.x + matrix[1][1] * in.y + matrix[2][2]);
    return new Point(newX, newY);
  }
  
//  public abstract void bloopity();
}

Translate.java

package lecture07;

public class Translate extends Transform {
  public Translate(double dx, double dy) {
    super();
    matrix[0][0] = matrix[1][1] = matrix[2][2] = 1.0;
    matrix[0][2] = dx;
    matrix[1][2] = dy;
  }
}

Scale.java

package lecture07;

public class Scale extends Transform {
  public Scale(double sx, double sy) {
    super();
    matrix[0][0] = sx;
    matrix[1][1] = sy;
    matrix[2][2] = 1.0;
  }
}

Rotate.java

package lecture07;

public class Rotate extends Transform {
  public Rotate(double radians) {
    super();
    matrix[0][0] = Math.cos(radians);
    matrix[0][1] = -Math.sin(radians);
    matrix[1][0] = Math.sin(radians);
    matrix[1][1] = Math.cos(radians);
    matrix[2][2] = 1.0;
  }
}

DotMover.java

package lecture07;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class DotMover extends JFrame implements MouseWheelListener, MouseListener, MouseMotionListener {
  private ArrayList<Point> points;
  private ArrayList<Transform> xforms;
  private DotPanel panel;
  private Point mouseLastAt;
  
  public DotMover() {
    super("DotMover");
    
    points = new ArrayList<Point>();
    for (int i = 0; i < 1000; i += 20) {
      points.add(new Point(30 + i, 30));
    }
    xforms = new ArrayList<Transform>();
    
//    xforms.add(new Rotate(Math.PI / 4));
//    xforms.add(new Translate(100, 50));
//    xforms.add(new Scale(3, 1));
    
    panel = new DotPanel();
    add(panel, BorderLayout.CENTER);

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(1024, 600);
    setVisible(true);
    
    addMouseListener(this);
    addMouseMotionListener(this);
    addMouseWheelListener(this);
  }
  
  public class DotPanel extends JPanel {
    @Override
    protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      
      Random r = new Random(101);
      for (Point p : points) {
        
        for (Transform t : xforms) {
          p = t.apply(p);
        }
        
        g.setColor(new Color(r.nextFloat(), r.nextFloat(), r.nextFloat()));
        g.drawOval(p.x, p.y, 5, 5);
      }
    }
  }

  public static void main(String[] args) {
    new DotMover();
  }

  @Override
  public void mouseWheelMoved(MouseWheelEvent event) {
//    xforms.add(new Scale(event.getWheelRotation() / 20.0, event.getWheelRotation() / 20.0));
    panel.repaint();
  }

  @Override
  public void mouseDragged(MouseEvent event) {
    Point mouseNowAt = event.getPoint();
    int diffY = mouseNowAt.y - mouseLastAt.y;
    xforms.add(new Rotate(diffY / 100.0));
    mouseLastAt = mouseNowAt;
    panel.repaint();
  }

  @Override
  public void mouseMoved(MouseEvent arg0) {
  }

  @Override
  public void mouseClicked(MouseEvent arg0) {
  }

  @Override
  public void mouseEntered(MouseEvent arg0) {
  }

  @Override
  public void mouseExited(MouseEvent arg0) {
  }

  @Override
  public void mousePressed(MouseEvent event) {
    mouseLastAt = event.getPoint();
  }

  @Override
  public void mouseReleased(MouseEvent arg0) {
  }
}

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