Chapter 16: Example 16-12: Simple Background Removal

// 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();
}