Shiffman's Mirror

// Learning Processing by Daniel Shiffman

// http://www.learningprocessing.com

// Example 16-6: Drawing a grid of squares

// "Brightness Mirror"

​

// videoScale is the size of each cell in the grid, 

// and the ratio of canvas size to video capture size

// 40 * 16 = 640

// 30 * 16 = 480

var videoScale = 16;

​

// Number of columns and rows in our system

var cols, rows;

​

function setup() {

  createCanvas(640, 480);

​

  // Initialize columns and rows

  cols = width/videoScale;

  rows = height/videoScale;

​

  pixelDensity(1);

  video = createCapture(VIDEO);

  video.size(cols, rows);

  video.hide();

}

​

function draw() {

  background(0);

  rectMode(CENTER);

  video.loadPixels();

​

  // Begin loop for columns

  for (var i = 0; i < cols; i++) {

    // Begin loop for rows

    for (var j = 0; j < rows; j++) {

      // Reversing x to mirror the image

      // In order to mirror the image, the column is reversed with the following formula:

      // mirrored column = width - column - 1

      var loc = ((cols - i - 1) + j * cols) * 4;

      // The functions red(), green(), and blue() 

      // extract these color components from a pixel.

      var r = video.pixels[loc    ]; 

      var g = video.pixels[loc + 1];

      var b = video.pixels[loc + 2];

​

      // A rectangle size is calculated as a function of the pixel's brightness. 

      // A bright pixel is a large rectangle, and a dark pixel is a small one.

      var sz = map((r+g+b)/3, 0, 255, 0, videoScale);

      fill(255);

      noStroke();

      // For every column and row, a rectangle is drawn at an (x,y) location scaled and sized by videoScale.

      var x = i*videoScale;

      var y = j*videoScale;

      rect(x + videoScale/2, y + videoScale/2, sz, sz);

    }

  }

}