Can anyone help me!
I am new to Java 2D and I am trying to drawing circles on an image.
At the moment I am using BufferedImage and trying to use the technique,
'Double Buffering'
The 'Double Buffering' was meant to prevent any flickering, but when I
click the mouse the image to add a circle, the display flickers.
Can anyone point out my errors or provide me with some better code
Thanx
David
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import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.awt.geom.Ellipse2D ;
import java.io.*;
import java.util.Stack ; // Use for the Stack class
import com.sun.image.codec.jpeg.*;
public class DrawCirclesOnImage extends Component {
private String imageToLoad ;
private BufferedImage imgOffScreenJPEG;
private BufferedImage bufferImage ;
private Stack coordsStack ;
private int coordsCount ;
public DrawCirclesOnImage( String file ) {
coordsCount = 0 ;
imageToLoad = file ;
coordsStack = new Stack() ;
}
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D)g;
// If the offscreen image is not defined, create it.
if (imgOffScreenJPEG == null)
createOffscreenImage();
Dimension d = getSize();
int w = d.width, h = d.height;
bufferImage = new BufferedImage( w, h, BufferedImage.TYPE_INT_RGB ) ;
bufferImage = makeBufferedImage( imgOffScreenJPEG,
BufferedImage.TYPE_INT_RGB ) ;
drawGPSObjects( ( Graphics2D )bufferImage.getGraphics() ) ;
g2.drawImage( bufferImage, null, null );
}
private void createOffscreenImage() {
// Create a BufferedImage the same size as this component.
Dimension d = getSize();
int w = d.width, h = d.height;
imgOffScreenJPEG = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB ) ;
// Obtain the Graphics2D for the offscreen image.
Graphics2D g2 = imgOffScreenJPEG.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
// Load an image from a file.
try {
InputStream in = getClass().getResourceAsStream(imageToLoad);
JPEGImageDecoder decoder = JPEGCodec.createJPEGDecoder(in);
BufferedImage image = decoder.decodeAsBufferedImage();
in.close();
// Draw the loaded image on the offscreen image.
g2.drawImage(image, 0, 0, w, h, null);
}
catch (Exception e) {
System.out.print(e);
}
}
private void drawGPSObjects( Graphics2D g2 ) {
int OBJECT_CIRCLE_SIZE = 60 ;
Stack tempStack = ( Stack )coordsStack.clone() ;
Dimension tempDim ;
// Set composite so that circles are draw half see-through
g2.setComposite( AlphaComposite.getInstance( AlphaComposite.SRC_OVER,
( float )0.3 ) ) ;
while( !tempStack.isEmpty() ) {
tempDim = new Dimension( ( Dimension )tempStack.pop() ) ;
Ellipse2D e = new Ellipse2D.Double( tempDim.width - (
OBJECT_CIRCLE_SIZE / 2),
tempDim.height - ( OBJECT_CIRCLE_SIZE / 2 ),
OBJECT_CIRCLE_SIZE, OBJECT_CIRCLE_SIZE ) ;
g2.setPaint( Color.red ) ;
g2.fill( e ) ;
g2.draw( e ) ;
}
// Reset composite
g2.setComposite( AlphaComposite.getInstance( AlphaComposite.SRC_OVER ) ) ;
}
public void addCoordinate( int x, int y ) {
if( coordsCount == 10 )
return ;
Dimension coords = new Dimension( x, y ) ;
coordsStack.push( coords ) ;
coordsCount++ ;
repaint() ;
}
public void update( Graphics g ) {
paint( g ) ;
}
private BufferedImage makeBufferedImage( Image image, int imageType ) {
BufferedImage bImage = new BufferedImage( image.getWidth(null),
image.getHeight(null), imageType ) ;
Graphics2D g2 = bImage.createGraphics() ;
g2.drawImage( image, null, null ) ;
return bImage ;
}
}
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