BufferedImage image = new BufferedImage(width,height,BufferedImage.INT_RGB);

Int[] imagePixelData = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();

...

// main loop start
while (true)
{


/// do stuff...


for (int y=0;y<height;y++)
{
for (int x=0;x<width;x++)
{

// get red, green, blue components however you like

imagePixelData[y*width+x] = red<<16 | green <<8 | blue;
}
}


// get graphic object of swing component to draw on and draw the image
g.drawImage(image,0,0,null);

// go back to start of main loop
}

import java.awt.Graphics2D;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;

import javax.swing.JFrame;

final public class a extends JFrame
{
   private static final int SCREEN_WIDTH = 1024;                     // Screen Width
   private static final int SCREEN_HEIGHT = 768;                     // Screen Height
   private static final int WIDTH_MUL_HEIGHT_MINUS_ONE=SCREEN_WIDTH*SCREEN_HEIGHT-1;
   
    final public static  void main( String[] a) throws Exception
    {
         new a();
    }
        
    a() throws Exception
    {

         Graphics2D g; 
      final BufferedImage image= new BufferedImage(SCREEN_WIDTH,SCREEN_HEIGHT,BufferedImage.TYPE_INT_RGB);
      
/****************************************************************************************************************
 * Initalize Screen
 */
      // the buffer strategey used for the video double buffer
      BufferStrategy strategy;
       
      setSize(SCREEN_WIDTH, SCREEN_HEIGHT); 
      show();
      
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      
      createBufferStrategy(2);
      strategy = getBufferStrategy();
      
       int frameCount=0;
      long threashold=System.currentTimeMillis();
      long time;
      int i;
      
      int[] pixelData=((DataBufferInt)image.getRaster().getDataBuffer()).getData();

      /****************************************************************************************************************
       * Game Loop
       */
      do
      {      
         time=System.currentTimeMillis();   // the current timestamp
         frameCount++;
          if(time>threashold)
          {
             setTitle(""+frameCount);
             frameCount=0;
             threashold=time+1000-(time-threashold);
          }
          
          for (i=WIDTH_MUL_HEIGHT_MINUS_ONE;i>=0;i--)
          {
             pixelData[i]=(i)&0xFFFFFF;
          }
          
          
          
           // Get hold of a graphics context for the accelerated surface
           g = (Graphics2D) strategy.getDrawGraphics();
         g.drawImage(image,0,0,null);
         
          strategy.show();
      
      //    // give some cpu time to other processes
          Thread.yield();
      } while (true);
         
    }
    
}
   

ImageBuffer buffer = new ImageBuffer(1024,768);
byte[] pixelData = buffer.getRGBA() ;
Image image = buffer.getImage();

...

int index;

// main loop
while(true)
{

for (int y=0;y<height;y++)
{

for (int x=0;x<width;x++)
{
   index=(y*width+x)*4;
   pixelData[index++]=red_component
   pixelData[index++]=green_component
   pixelData[index++]=blue_component
   pixelData[index]=alpha_component
}
}

...

draw image to canvas

}