How to Draw Constantly Changing Graphics in Java
Introduction
Creating dynamic graphics that update constantly can be a challenging task in Java. In this article, we will demonstrate how to tackle this using efficient techniques and thread synchronization.
Problem Statement
The initial code provided in the question had several performance issues, resulting in slow graphic updates. The goal is to optimize the code to achieve constant updates with improved speed.
Optimized Code
Here's an optimized version of the code:
import javax.swing.*; import java.awt.*; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.awt.geom.Ellipse2D; import java.awt.image.BufferedImage; public class ZoomPanel extends JPanel { private static final int STEP = 40; private int iter = 0; private long cumulativeTimeTaken = 0; // Model to hold pixel colors private final Color[][] model = new Color[8][8]; // Flag to prevent concurrent painting private boolean isDrawing = false; public static void main(String[] args) { final JFrame frame = new JFrame("Image zoom"); final ZoomPanel zoomPanel = new ZoomPanel(); frame.getContentPane().add(zoomPanel); final Ticker t = new Ticker(zoomPanel); frame.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent we) { t.done(); frame.dispose(); } }); t.start(); frame.setLocation(new Point(640, 0)); frame.pack(); frame.setVisible(true); } // Sets the pixel color at the given position private void setColorAt(int x, int y, Color pixelColor) { model[x][y] = pixelColor; repaint(40 + x * STEP, 45 + y * STEP, 40 + (x * STEP) - 3, 45 + (y * STEP) - 3); } // Gets the pixel color at the given position private Color getColorAt(int x, int y) { return model[x][y]; } // Draws the graphics public void paintComponent(Graphics g) { long start = System.currentTimeMillis(); if (!SwingUtilities.isEventDispatchThread()) { throw new RuntimeException("Repaint attempt is not on event dispatch thread"); } // Prevent concurrent painting isDrawing = true; final Graphics2D g2 = (Graphics2D) g; g2.setColor(getBackground()); try { for (int x = 0; x < 8; x++) { for (int y = 0; y < 8; y++) { g2.setColor(model[x][y]); Ellipse2D e = new Ellipse2D.Double(40 + x * STEP, 45 + y * STEP, STEP - 3, STEP - 3); g2.fill(e); g2.setColor(Color.GRAY); g2.draw(e); } } } catch (Exception e) { e.printStackTrace(); } iter++; // Display FPS count g2.setColor(Color.black); long stop = System.currentTimeMillis(); cumulativeTimeTaken += stop - start; StringBuilder sb = new StringBuilder(); sb.append(iter) .append(" frames in ") .append((double) (cumulativeTimeTaken) / 1000) .append("s."); System.out.println(sb); // Allow painting again isDrawing = false; } private static class Ticker extends Thread { private final Robot robot; public boolean update = true; private final ZoomPanel view; public Ticker(ZoomPanel zoomPanel) { view = zoomPanel; try { robot = new Robot(); } catch (AWTException e) { throw new RuntimeException(e); } } public void done() { update = false; } public void run() { int runCount = 0; while (update) { runCount++; if (runCount % 100 == 0) { System.out.println("Ran ticker " + runCount + " times"); } final Point p = MouseInfo.getPointerInfo().getLocation(); Rectangle rect = new Rectangle(p.x - 4, p.y - 4, 8, 8); final BufferedImage capture = robot.createScreenCapture(rect); // Synchronized block to prevent concurrent access to the model synchronized (view) { // If the panel is not drawing, update the model and repaint if (!view.isDrawing) { for (int x = 0; x < 8; x++) { for (int y = 0; y < 8; y++) { final Color pixelColor = new Color(capture.getRGB(x, y)); if (!pixelColor.equals(view.getColorAt(x, y))) { final int finalX = x; final int finalY = y; SwingUtilities.invokeLater(new Runnable() { public void run() { view.setColorAt(finalX, finalY, pixelColor); } }); } } } } } } } } }
Improvements
These optimizations result in a vast improvement in performance, with the screen updates appearing virtually instantaneous. The FPS counter provides a measure of the improved speed.
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