Slick Forums

class _ extends BasicGame{
    ...
    public void render(GameContainer gc, Graphics g) throws SlickException{
        myObj.myRender();
    }
}

class myObj{
    Image image;
    ...
    public void myRender() throws SlickException{
        image.getGraphics().setDrawMode(Graphics.MODE_ADD);
        image.draw(x, y);
        image.getGraphics().setDrawMode(Graphics.MODE_NORMAL);
    }
}

Image offscreen;
Graphics offscreenGraphics;
boolean offscreenDirty = true;

public void init(GameContainer c) throws SlickException {
   //memory leak with current Slick build, see here:
   //http://slick.javaunlimited.net/viewtopic.php?f=1&t=4511
   offscreen = new Image(256, 256);
   offscreenGraphics = offscreen.getGraphics();
}

public void render(GameContainer c, Graphics g) throws SlickException {
   //ideally, we only render to our offscreen image
   //when it's dirty and needs updating. this saves
   //us needing to update it every frame
   if (offscreenDirty) {
      offscreenDirty = false;
      updateOffscreen();
   }
   
   //render the image
   g.drawImage(offscreen);
}

public void updateOffscreen() {
   //clear the image so that we start fresh
   offscreenGraphics.clear();
   //draw another image on this offscreen buffer   
   offscreenGraphics.drawImage(myOtherImage, 0, 0);
   //and do whatever else here...
   //...
   
   //finally, flush the graphics
   offscreenGraphics.flush();
}