// Video Difference Engine
//
//  Scott "Jerry" Lawrence
//  2003-08-27

boolean newFrame = false; // was there a new frame?
float[] prvframe = new float[320*240];  // the previous frame

int thresh = 50; // difference threshhold
float fadeval = 2/3; // how quickly the video fades

// our initialization
void setup()
{
  size( 320, 240 ); // screen size
  noBackground(); // don't clear the backing store with each frame
  beginVideo( width, height, 30 ); // start up video capture

  // clear the previous frame
  color black = color( 0,0,0 );
  for( int i=0 ; i<width*height; i++ )
  {
    prvframe[i] = black;
  }
}

// handle a video event
void videoEvent()
{
  newFrame = true;
}

// the main loop...
void loop()
{
  if(newFrame)
  {
    for( int i=0 ; i < width*height ; i++ )
    {
      float vidbrt = brightness( video.pixels[i] );
      float prvbrt = prvframe[i];
      
      if( abs( vidbrt - prvbrt) >= thresh )
      {
        // blit over the pixels if they're above the threshhold
        pixels[i] = video.pixels[i];
      } else {
        // fade out the ones that are stagnant.
        pixels[i] = color(
                      red(pixels[i])*fadeval,
                      green(pixels[i])*fadeval,
                      blue(pixels[i])*fadeval
                    );
      }
      
      prvframe[i] = vidbrt;
    }
    newFrame = false;
  }
}