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Slight change of https://editor.p5js.org/michaelshiloh/sketches/ZqXC5-6M0

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let camera0;    // the camera0 object

let arraySize; // global to avoid recalculating 

                // every frame

let previous_frame = []; // the previous frame

let threshold = 100;

​

function setup() {

  createCanvas(400, 400);

  pixelDensity(1);

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  camera0 = createCapture(VIDEO);

  camera0.size(400, 400);

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  // Number of pixels is the dimensions of the 

  // input device, and each pixel has 4 

  // components (red, green, blue, alpha)

  arraySize = camera0.width * camera0.height * 4;

  // Initialize the previous frame to blank

  for (let i = 0; i < arraySize; i++) {

    previous_frame.push = 0;

  }

​

  camera0.hide();

}

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function draw() {

  background(0)

  // Get the pixel array from the camera0

  camera0.loadPixels(); 

  // Get the pixel array from the canvas

  loadPixels();

​

  let curr_r, curr_g, curr_b; 

  let prev_r, prev_g, prev_b;

  let diff_r, diff_g, diff_b; // computed differences

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  // For each pixel in the video frame

  for (let i = 0; i < arraySize; i += 4) {

    // Extract the red, green, and blue 

    // components from both the current 

    // and the previous pixel color

    curr_r = camera0.pixels[i + 0];

    curr_g = camera0.pixels[i + 1];

    curr_b = camera0.pixels[i + 2];

    prev_r = previous_frame[i + 0];

    prev_g = previous_frame[i + 1];

    prev_b = previous_frame[i + 2];

​

    // And calculate the differences

    diff_r = abs(curr_r - prev_r); 

    diff_g = abs(curr_g - prev_g); 

    diff_b = abs(curr_b - prev_b);

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    // If difference is greater than threshold, set the pixel white

    let pixelColor = ((diff_r+diff_g+diff_b)>threshold) ? 255:0;

    pixels[i + 0] = pixelColor;

    pixels[i + 1] = pixelColor;

    pixels[i + 2] = pixelColor;

    // The current pixel becomes 

    // the previous pixel for the next frame

    previous_frame[i + 0] = curr_r;

    previous_frame[i + 1] = curr_g;

    previous_frame[i + 2] = curr_b;

  }

  // Write the pixels array to the canvas

  updatePixels(); 

}

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