Java Tutorial/2D Graphics/Buffer Paint

Double buffer

   <source lang="java">

import java.applet.Applet; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Image; import java.awt.event.MouseEvent; import java.awt.event.MouseMotionAdapter; import java.awt.image.BufferedImage; import javax.swing.JFrame; public class DoubleBufferWithBufferedImage extends Applet {

 int gap = 3;
 int mx, my;
 Image buffer = null;
 int w, h;
 public static void main(String[] a) {
   JFrame f = new JFrame();
   f.setSize(300, 300);
   f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   f.getContentPane().add(new DoubleBufferWithBufferedImage());
   f.setVisible(true);
 }
 public DoubleBufferWithBufferedImage() {
   setSize(300, 300);
   Dimension d = getSize();
   w = d.width;
   h = d.height;
   buffer = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
 }
 public void paint(Graphics g) {
   Graphics screengc = null;
   screengc = g;
   g = buffer.getGraphics();
   g.setColor(Color.blue);
   g.fillRect(0, 0, w, h);
   g.setColor(Color.red);
   for (int i = 0; i < w; i += gap)
     g.drawLine(i, 0, w - i, h);
   for (int i = 0; i < h; i += gap)
     g.drawLine(0, i, w, h - i);
   screengc.drawImage(buffer, 0, 0, null);
 }

}</source>

Off Screen Paint: create Graphics from BufferedImage

   <source lang="java">

import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.RenderingHints; import java.awt.geom.Arc2D; import java.awt.image.BufferedImage; import javax.swing.JComponent; import javax.swing.JFrame; class MyCanvas extends JComponent {

 private BufferedImage offImg;
 public void draw(Graphics g) {
   Graphics2D g2 = (Graphics2D) g;
   // Draw the pie chart
   Arc2D.Float arc = new Arc2D.Float(Arc2D.PIE);
   arc.setFrame(140, 200, 67, 46);
   arc.setAngleStart(45);
   arc.setAngleExtent(270);
   g2.setColor(Color.gray);
   g2.draw(arc);
   g2.setColor(Color.red);
   g2.fill(arc);
   g2.setColor(Color.black);
   g2.drawString("Arc2D.PIE", 140, 190);
 }
 public Graphics2D createDemoGraphics2D(Graphics g) {
   Graphics2D g2 = null;
   if (offImg == null || offImg.getWidth() != getSize().width
       || offImg.getHeight() != getSize().height) {
     offImg = (BufferedImage) createImage(getSize().width, getSize().height);
   }
   if (offImg != null) {
     g2 = offImg.createGraphics();
     g2.setBackground(getBackground());
   }
   // .. set attributes ..
   g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

   // .. clear canvas ..
   g2.clearRect(0, 0, getSize().width, getSize().height);
   return g2;
 }
 public void paint(Graphics g) {
   if (getSize().width <= 0 || getSize().height <= 0)
     return;
   Graphics2D g2 = createDemoGraphics2D(g);
   draw(g2);
   g2.dispose();
   if (offImg != null && isShowing()) {
     g.drawImage(offImg, 0, 0, this);
   }
 }

} public class OffScreenPaint {

 public static void main(String[] a) {
   JFrame window = new JFrame();
   window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   window.setBounds(30, 30, 300, 300);
   window.getContentPane().add(new MyCanvas());
   window.setVisible(true);
 }

}</source>