I've gotten the program to locate the brightest pixel through code found somewhere on the forums (but that is unreliable because it keeps moving around), I don't understand how to extend it so that it tells me the brightest chunk. Rather than finding the brightest pixel, it should find the brightest 5x5 for instance. 

Here's what I have:

Hi

I'm trying to write a program that will be able to plot the angle of a pendulum versus time. The program so far detects the bottom of the pendulum by detecting the brightest pixel on screen (the pendulum has an LED attached). I've drawn a stationary ellipse as the starting position of the pendulum. 

I have gotten the program to determine theta based on the initial postion. I now have to plot theta versus time and do not know how to do this. I started making an array to record the x,y values but don't know where to go from there. I can print them using the println() command but I want a live plot of theta versus time. My programming knowledge is very basic so please be specific. 

import processing.video.*;

Capture video;

lightPoint point1;

void setup() {

  size(640, 480); 

  video = new Capture(this, width, height, 30);

  noStroke();

  smooth();

  //Create a light point to visualise from the class lightPoint

  point1 = new lightPoint(0.0, 0.0, 0);

}

void draw() {

  if (video.available()) {

    video.read();

    image(video, 0, 0, width, height); // Draw the webcam video onto the screen

    int brightestX = 0; // X-coordinate of the brightest video pixel

    int brightestY = 0; // Y-coordinate of the brightest video pixel

    float brightestValue = 0; // Brightness of the brightest video pixel

    // Search for the brightest pixel: For each row of pixels in the video image and

    // for each pixel in the yth row, compute each pixel's index in the video

    video.loadPixels();

    int index = 0;

    for (int y = 0; y < video.height; y++) {

      for (int x = 0; x < video.width; x++) {

        // Get the color stored in the pixel

        int pixelValue = video.pixels[index];

        // Determine the brightness of the pixel

        float pixelBrightness = brightness(pixelValue);

        // If that value is brighter than any previous, then store the

        // brightness of that pixel, as well as its (x,y) location

        if (pixelBrightness > brightestValue) {

          brightestValue = pixelBrightness;

          brightestY = y;

          brightestX = x;

          point1.x = brightestX;

          point1.y = brightestY;

        }

        index++;

      }

      ellipse(320, 150, 25, 25);

      

      

      float[]x = new float[1000];

      float[]y = new float[1000];

      float[][]xy = {

      println(atan(abs(point1.x-320)/abs(point1.y-150)));

    }

    // Display the lightPoint objects

    // ellipse(brightestX, brightestY, 50, 50);

    point1.display();

    // draw_grid(brightestX, brightestY);

  }

}

float[] values = new float[width];

class lightPoint {

  float x = 0.0; // X-coordinate of the brightest video pixel

  float y = 0.0; // Y-coordinate of the brightest video pixel

  // float brightestValue = 0; // Brightness of the brightest video pixel

  boolean selected = false;

  int index;

  lightPoint(float xpos, float ypos, int num) {

    x = xpos;

    y = ypos;

    index = num;

    selected = false;

  }

  void display() {

    fill(204,102,0);

    ellipse(x, y, 25, 25);

  }

}