[java] Graphics buffers

import java.awt.*;

public class GraphApplet extends java.applet.Applet
{
  int numberOfLines =100;
  Graphics bufferg;  // Sets bufferg for graphic use
  Image buffer;  // Image to be used to draw next frame,
  public Image newPic;
  int[] linesY = new int[numberOfLines];
  int[] linesTrueLen =  new int[numberOfLines];
  int[] linesLength =  new int[numberOfLines];
  boolean change  = true;

  public void init()
  {
    setBackground(Color.cyan);
    for (int i = 0 ; i     {
	linesLength = i;
	linesY[i] = i;
	linesTrueLen[i] = -1;
    }

    for (int i = 0 ; i     {
	while(linesTrueLen[i] == -1)
	{
	  int pickNum =  (int)(100*Math.random());
  	  linesTrueLen[i] = linesLength[pickNum];
          linesLength[pickNum] =-1;
        }
    }
    buffer  = createImage(getSize().width , getSize().height);//Createsthe next frame to be displayed
    bufferg = buffer.getGraphics();//Calls the back frame
  }
  public void update(Graphics g)
  {
    paint(bufferg);  // Updates paint
    g.drawImage(buffer , 0, 0, this);// Draws the next frame
  }

  public void paint(Graphics g)
  {
    if(!change)
      System.exit(0);
    int holdLength ;
    change  = false;
    g.clearRect(0,0,getSize().width, getSize().height);
    g.setColor(Color.black);

    for (int i = 0 ; i       g.drawLine(0,linesY[i],linesTrueLen[i],linesY[i]);

    for (int i =0 ; i     {
      if(linesTrueLen[i+1]      {
        holdLength = linesTrueLen[i+1];
        linesTrueLen[i+1] = linesTrueLen[i];
        linesTrueLen[i]= holdLength ;
        change = true;
      }
     }

   try
   {
     Thread.sleep(100);
   }
   catch(InterruptedException e){}
   repaint();
  }

}
 

Hope this helps.
PS: You should look for the update() method

Ok, so let''s say I create the following:

Graphics graphBuffer;
Image buffer;
int rows, cols;
int pixels[];
pixels = new int[cols][rows];

I make my own fillRect and text drawing methods to write the pixel values into the array, then use:

buffer = createImage(new MemoryImageSource(cols, rows, pixels, 0, cols));

To make the buffer from the array of pixels. Would this work? If so, how fast would this be? As long as it doesn''t slow the applet down a lot, I''m fine. I''m just trying to get rid of a flicker, and I''m thinking this will work. If I''m wrong, or you have a better idea than I do, let me know.

I looked up a few things about Image and saw how you were drawing without using the pixel array. Thanks for the help.

btw: Ignore my last post, I don''t need to do that anymore.

I''m not sure what I''m doing wrong, but here is what I''m doing in my code:

private Graphics gBuffer;
private Image buffer;

public void init()
{
buffer = karelGraphics.createImage(numCols, numRows);
gBuffer = buffer.getGraphics();
} // end init

public void paint()
{
// drawing using gBuffer

g.drawImage(buffer, 0, 0, this);
}

So, what am I doing wrong?

Here is how I draw my graphics in applets I hope it helps









[edited by - wrathnut on December 18, 2002 11:19:37 PM]

I had the same steps you do, but for some reason it wouldn''t run initialize the offScreenImage and offScreenGraphics in init(). I fixed it, so all is well now =). Thanks for your help.

The best way to do rendering is with BufferedStategy.

http://java.sun.com/docs/books/tutorial/extra/fullscreen/

It takes care of the hassle of managing VolatileImage buffers, and gives you easy access to video memory.

Harley.