sample script using processing + syphon

processing_syphon.pde

import codeanticode.syphon.*;
PGraphics canvas;
SyphonServer server;

PImage img;

void setup() {
  size(1600,900, P3D);
  canvas = createGraphics(1600, 900, P3D);
  server = new SyphonServer(this, "Processing Syphon");  
}

void draw(){
  canvas.beginDraw();
  canvas.background(100);
  canvas.stroke(255);
  canvas.line(50, 50, mouseX, mouseY);
  canvas.endDraw();
  image(canvas, 0, 0);
  server.sendImage(canvas);
}