HandTrail.java

// HandTrail.java
// Andrew Davison, November 2011, ad@fivedots.psu.ac.th

/* Store hand coordinates in a list (up to a maximum of MAX_POINTS)
 and draw them as a trail (actually a polyline).

 When MAX_POINTS is reached, the oldest point (at position 0) is
 discarded, causing the rendering to show a trail of previous hand
 points.
 */

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.Point;
import java.util.ArrayList;
import java.util.List;

import org.OpenNI.DepthGenerator;
import org.OpenNI.Point3D;
import org.OpenNI.StatusException;

public class HandTrail {
    private static final int MAX_POINTS = 20;

    private static final int CIRCLE_SIZE = 20;
    private static final int STROKE_SIZE = 15;

    private static final Color POINT_COLORS[] = { Color.RED, Color.BLUE, Color.CYAN, Color.GREEN, Color.MAGENTA, Color.PINK, Color.YELLOW };

    private Font msgFont; // for the hand ID string

    private int handID;
    private DepthGenerator depthGen;
    private List<Point> coords; // the points that form the trail

    public HandTrail(int id, DepthGenerator dg) {
	handID = id;
	depthGen = dg;
	msgFont = new Font("SansSerif", Font.BOLD, 24);

	coords = new ArrayList<Point>();
    } // end of HandTrail()

    public synchronized void addPoint(Point3D realPt)
    // add hand coordinate to the coords list
    {
	try {
	    Point3D pt = depthGen.convertRealWorldToProjective(realPt);
	    // convert real-world coordinates to screen form
	    if (pt == null)
		return;
	    coords.add(new Point((int) pt.getX(), (int) pt.getY())); // discard
								     // z coord
	    if (coords.size() > MAX_POINTS) // get rid of the oldest point
		coords.remove(0);
	} catch (StatusException e) {
	    System.out.println("Problem converting point");
	}
    } // end of addPoint()

    public synchronized void draw(Graphics2D g2)
    /*
     * draw trail and large circle on hand (the last point) with the hand ID in
     * the center
     */
    {
	int numPoints = coords.size();
	if (numPoints == 0)
	    return;

	drawTrail(g2, coords, numPoints);

	// draw large circle on hand (the last point)
	Point pt = coords.get(numPoints - 1);
	g2.setColor(POINT_COLORS[(handID + 1) % POINT_COLORS.length]);
	g2.fillOval(pt.x - CIRCLE_SIZE / 2, pt.y - CIRCLE_SIZE / 2, CIRCLE_SIZE, CIRCLE_SIZE);

	// draw the hand ID
	g2.setColor(Color.WHITE);
	g2.setFont(msgFont);
	g2.drawString("" + handID, pt.x - 6, pt.y + 6); // roughly centered
    } // end of draw()

    private void drawTrail(Graphics2D g2, List<Point> coords, int numPoints)
    // draw (x,y) Points list as a polyline (trail)
    {
	int[] xCoords = new int[numPoints];
	int[] yCoords = new int[numPoints];

	// fill the integer arrays for x and y points
	Point pt;
	for (int i = 0; i < numPoints; i++) {
	    pt = coords.get(i);
	    xCoords[i] = pt.x;
	    yCoords[i] = pt.y;
	}

	g2.setColor(POINT_COLORS[handID % POINT_COLORS.length]);
	g2.setStroke(new BasicStroke(STROKE_SIZE));

	// System.out.println("No of draw points: " + numPoints);
	g2.drawPolyline(xCoords, yCoords, numPoints);
    } // end of drawTrail()

} // end of HandTrail class