Im trying to check for motion in specific areas. The code below doesnt work but Im unsure why, any help would be greatly appreciated. Basically Im comparing the live video to a still image. If there is a difference above or below the X/Y used to be compared (via dist function) to a hotspot. The main problem seems to be getting the pixelY variable... (im using code adapted from a sketch on openprocessing)

Any ideas would be appreciated!

import processing.video.*;
Capture video;
int th = 140;
PImage room; //this is the image that is used check the differences with the live image
 int node1x = 40;
int node1y = 40;
int radius = 40;
void setup(){
  
  size(640,480);
  video = new Capture(this, width, height, 25); //here begins a new sessions of capturing of the images from the webcam
  room = loadImage("room.png");
video.start();
//noStroke();
smooth();
}

 
 
void draw(){
  background(255);
  if (video.available()) {
  video.read();
}

int myX = 0;
int myY = 0;
      loadPixels();

     int pixelX = -1, pixelY = -1;
     

     video.loadPixels(); //fill an array of pixels from the current captured image
         room.loadPixels(); //fill an array of pixels from the current captured image

     for(int i=0; i<video.height*video.width; i++){ //read every element of the pixels array
      
        pixelX = i % width;                                                            //get the real pixel X position
        
        if( pixelX != width ) {
          pixelY = ( i / width ) +1;
        } else {
          pixelY = ( i / height );
        }  //get the real pixel Y position

if(brightness(video.pixels[i]) < brightness(room.pixels[i])-th || brightness(video.pixels[i]) > brightness(room.pixels[i])+th ) {
myX = pixelX;
myY = pixelY;
}
     
} // END VIDEO SCAN LOOP
updatePixels();

if (dist(myX, myY, node1x, node1y) < radius) {
  //VISUAL FEEDBACK
  ellipseMode(CENTER);
  fill(255, 0, 0);
  ellipse(node1x, node1y, 20, 20);
}
  println(myX + "   " + myY);
// END
}