simple IPimage to PDF doesn't work

Hi all,

I'm testing out a code snippet which is to be integrated into a big sketch. I just want to test the image quality of the image inside a pdf. It will later be combined with vector output. Here's the code:

1. PImage img;
2. import processing.pdf.*;
3. PGraphicsPDF my_pdf;
4. void setup(){
5.   size(500, 375);
6.   img = loadImage("15.jpg");
7.   image(img, 0, 0);
8.   my_pdf = (PGraphicsPDF)createGraphics(500, 375, PDF, "img.pdf");
9.   my_pdf.beginDraw();
10.   my_pdf.dispose();
11.   my_pdf.endDraw(); // stop and save pdf
12.   //exit();
13. }
14. void draw(){
15. }

All I get is a blank pdf file...? Maybe I'm missing something basic here but the code works in another sketch. I also tried with the exit() activated.
I hope someone can help me go just get this image in a pdf. Thanks a lot in advance. Best, d