import processing.video.*;
  
  color black = color(0);
  color white = color(255);
  int numPixels;
  Capture video;
  
  void setup() {
    size(640, 480); // Change size to 320 x 240 if too slow at 640 x 480
    strokeWeight(5);
    // Uses the default video input, see the reference if this causes an error
    video = new Capture(this, width, height, 24);
    numPixels = video.width * video.height;
    noCursor();
    smooth();
  }
  
  void draw() {
    if (video.available()) {
      video.read();
      video.loadPixels();
      int threshold = 127; // Set the threshold value
      float pixelBrightness; // Declare variable to store a pixel's color
      // Turn each pixel in the video frame black or white depending on its brightness
      loadPixels();
      for (int i = 0; i < numPixels; i++) {
        pixelBrightness = brightness(video.pixels[i]);
        if (pixelBrightness > threshold) { // If the pixel is brighter than the
          pixels[i] = white; // threshold value, make it white
        } 
        else { // Otherwise,
          pixels[i] = black; // make it black
        }
      }
      updatePixels();
      // Test a location to see where it is contained. Fetch the pixel at the test
      // location (the cursor), and compute its brightness
      int testValue = get(mouseX, mouseY);
      float testBrightness = brightness(testValue);
      if (testBrightness > threshold) { // If the test location is brighter than
        fill(black); // the threshold set the fill to black
      } 
      else { // Otherwise,
        fill(white); // set the fill to white
      }
      ellipse(mouseX, mouseY, 20, 20);
    }
  }