I started working with NyARToolkit today. It seems the following does what you want...

1. SingleARTKMarker nya;
2. PImage cam;
3. 
   
4. void setup() {
5.   size(640,480,P3D);
6.   nya = new SingleARTKMarker(this,width,height,"camera_para.dat");
7.   nya.setARCodes("patt.hiro",80);
8.   cam = loadImage("input.jpg"); // load your image here
   
9. }
10. 
    
11. void draw() {
12.   background(255);
13.   nya.drawBackground(cam);
14.   switch(nya.detect(cam)){
15.   case SingleARTKMarker.ST_NOMARKER:
16.     return;
17.   case SingleARTKMarker.ST_NEWMARKER:
18.     println("Marker found.");
19.     return;
20.   case SingleARTKMarker.ST_UPDATEMARKER:
21.     break;
22.   case SingleARTKMarker.ST_REMOVEMARKER:
23.     println("Marker removed.");
24.     return;
25.   default:
26.     return;
27.   }
28.   nya.beginTransform();
29.     setMatrix(nya.getMarkerMatrix());
30.     drawBox();
31.   nya.endTransform();
32. }
33. 
    
34. void drawBox() {
35.   pushMatrix();
36.   fill(0);
37.   stroke(255,200,0);
38.   translate(0,0,20);
39.   box(40);
40.   noFill();
41.   translate(0,0,-20);
42.   rect(-40,-40,80,80);
43.   popMatrix();
44. }

The code works for me and you're not mentioning what's the error message. If it's a nullPointerException, you're not loading the image correctly. Try displaying the image before the nya-code to doublecheck the image loading has gone well. If it's something else, post the error message and the exact line it's running into this error.

thanks but its not working for me :(
can u help me with se same ideia but for java??
Thanks

Again, post the error message and the exact line it's running into this error.

      nya.drawBackground(cam);
The function drawBackground (Pimage) does not exist

but in trying to do the same but in java using eclipse could you help me in that

Download the correct library here.

If it's still not working, try putting NyAR4psg.jar and NyARToolkit.jar in a sketch subdirectory called code.

Read about using Eclipse here.

thanks, i have the last library but i dont know whats happening, even the example in the library its not working :( but i still tryin to do it, thanks again