// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 16-11: Simple color tracking
  
  import processing.video.*;
  
  // Variable for capture device
  Capture video;
  
  // A variable for the color we are searching for.
  color trackColor; 
  
  void setup() {
    size(320,240);
    video = new Capture(this,width,height,15);
    // Start off tracking for red
    trackColor = color(255,0,0);
    smooth();
  }
  
  void draw() {
    // Capture and display the video
    if (video.available()) {
      video.read();
    }
    video.loadPixels();
    image(video,0,0);
  
    // Before we begin searching, the "world record" for closest color is set to a high number that is easy for the first pixel to beat.
    float worldRecord = 500; 
  
    // XY coordinate of closest color
    int closestX = 0;
    int closestY = 0;
  
    // Begin loop to walk through every pixel
    for (int x = 0; x < video.width; x ++ ) {
      for (int y = 0; y < video.height; y ++ ) {
        int loc = x + y*video.width;
        // What is current color
        color currentColor = video.pixels[loc];
        float r1 = red(currentColor);
        float g1 = green(currentColor);
        float b1 = blue(currentColor);
        float r2 = red(trackColor);
        float g2 = green(trackColor);
        float b2 = blue(trackColor);
  
        // Using euclidean distance to compare colors
        float d = dist(r1,g1,b1,r2,g2,b2); // We are using the dist( ) function to compare the current color with the color we are tracking.
  
        // If current color is more similar to tracked color than
        // closest color, save current location and current difference
        if (d < worldRecord) {
          worldRecord = d;
          closestX = x;
          closestY = y;
        }
      }
    }
  
    // We only consider the color found if its color distance is less than 10. 
    // This threshold of 10 is arbitrary and you can adjust this number depending on how accurate you require the tracking to be.
    if (worldRecord < 10) { 
      // Draw a circle at the tracked pixel
      fill(trackColor);
      strokeWeight(4.0);
      stroke(0);
      ellipse(closestX,closestY,16,16);
    }
  }
  
  void mousePressed() {
    // Save color where the mouse is clicked in trackColor variable
    int loc = mouseX + mouseY*video.width;
    trackColor = video.pixels[loc];
  }