How to make an image transparent?

Question

Hi everybody,
I need to build a complex chart in my applet, for this I want at first to create some painted area and then to put a map over it. The map is an image, which consists basically of black lines for state borders, main rivers and lakes on the white background. What I need is to put just these black lines, not the white background which will kill previously painted area.
Can anyone give me an idea?
Thanks,
Alexandre

Answer 1

Here's a class that implements this. I need a "transparent" object that has a big red arrow that I can point at stuff, so it gets its parents context and paints that then paints the red arrow stuff. The only problem with this is that it is not a glass pane. The "transparent" object must be contained in one object so you can only "paint over" one object.
public class KiaTutorialArrow extends Panel
     public static final int WEST = 0, EAST = 1, NORTH = 2, SOUTH = 3;
     private int direction = 0;
     private Polygon arrow;
     //public Color foreground;;
     ////////constructors/////////////////////////////////////
     public KiaTutorialArrow()
          super();
          setSize(40,25);
     ////////////////get and set functions////////////////////
     public int getDirection()
          return direction;
     public void setDirection(int index)
          this.direction = index;
          arrow = null;
          repaint();
     public String getName()
          return super.getName();
     public void setName(String name)
          super.setName(name);
          repaint();
     public Color getBackground()
          return super.getBackground();
     public void setBackground(Color c)
          super.setBackground(c);
          repaint();
     public void paint(Graphics g)
          // TRANSPARENCY IS THE DEFAULT     
          Container c = getParent();
          Graphics graphics = g.create(- getLocation().x, - getLocation().y, c.size().width, c.size().height);
          c.paint(graphics);
          g.setColor(Color.red);
          switch (direction)
               case WEST: drawWest(g); break;
               case EAST: drawEast(g); break;
               case NORTH: drawNorth(g); break;
               case SOUTH: drawSouth(g); break;
               default: return;
     private void drawWest(Graphics g)
          if (arrow == null)
               arrow = new Polygon();
               arrow.addPoint(2,12);
               arrow.addPoint(12,5);
               arrow.addPoint(12,8);
               arrow.addPoint(27,8);
               arrow.addPoint(27,17);
               arrow.addPoint(12,17);
               arrow.addPoint(12,20);
          g.drawPolygon(arrow);
          g.fillPolygon(arrow);
     private void drawEast(Graphics g)
          if (arrow == null)
               arrow = new Polygon();
               arrow.addPoint(7,8);
               arrow.addPoint(22,8);
               arrow.addPoint(22,5);
               arrow.addPoint(32,12);
               arrow.addPoint(22,20);
               arrow.addPoint(22,17);
               arrow.addPoint(7,17);
          g.drawPolygon(arrow);
          g.fillPolygon(arrow);
     private void drawNorth(Graphics g)
          if (arrow == null)
               arrow = new Polygon();
               arrow.addPoint(8,0);
               arrow.addPoint(15,10);
               arrow.addPoint(12,10);
               arrow.addPoint(12,25);
               arrow.addPoint(3,25);
               arrow.addPoint(3,10);
               arrow.addPoint(0,10);
          g.drawPolygon(arrow);
          g.fillPolygon(arrow);
     private void drawSouth(Graphics g)
          if (arrow == null)
               arrow = new Polygon();
               arrow.addPoint(8,25);
               arrow.addPoint(0,15);
               arrow.addPoint(3,15);
               arrow.addPoint(3,0);
               arrow.addPoint(12,0);
               arrow.addPoint(12,15);
               arrow.addPoint(15,15);
          g.drawPolygon(arrow);
          g.fillPolygon(arrow);
}