// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 16-12: Simple background removal
  
  // Click the mouse to memorize a current background image
  import processing.video.*;
  
  // Variable for capture device
  Capture video;
  
  // Saved background
  PImage backgroundImage;
  
  // How different must a pixel be to be a foreground pixel
  float threshold = 20;
  
  void setup() {
    size(320,240);
    video = new Capture(this, width, height, 30);
    // Create an empty image the same size as the video
    backgroundImage = createImage(video.width,video.height,RGB);
  }
  
  void draw() {
    // Capture video
    if (video.available()) {
      video.read();
    }
    
    // We are looking at the video's pixels, the memorized backgroundImage's pixels, as well as accessing the display pixels. 
    // So we must loadPixels() for all!
    loadPixels();
    video.loadPixels(); 
    backgroundImage.loadPixels();
    
    // 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; // Step 1, what is the 1D pixel location
        color fgColor = video.pixels[loc]; // Step 2, what is the foreground color
        
        // Step 3, what is the background color
        color bgColor = backgroundImage.pixels[loc];
        
        // Step 4, compare the foreground and background color
        float r1 = red(fgColor);
        float g1 = green(fgColor);
        float b1 = blue(fgColor);
        float r2 = red(bgColor);
        float g2 = green(bgColor);
        float b2 = blue(bgColor);
        float diff = dist(r1,g1,b1,r2,g2,b2);
        
        // Step 5, Is the foreground color different from the background color
        if (diff > threshold) {
          // If so, display the foreground color
          pixels[loc] = fgColor;
        } else {
          // If not, display green
          pixels[loc] = color(0,255,0); // We could choose to replace the background pixels with something other than the color green!
        }
      }
    }
    updatePixels();
  }
  
  void mousePressed() {
    // Copying the current frame of video into the backgroundImage object
    // Note copy takes 5 arguments:
    // The source image
    // x,y,width, and height of region to be copied from the source
    // x,y,width, and height of copy destination
    backgroundImage.copy(video,0,0,video.width,video.height,0,0,video.width,video.height);
    backgroundImage.updatePixels();
  }