Simple Loop Frame Exporter

// This is a template for creating a looping animation in p5.js (JavaScript). 

// When you press the 'F' key, this program will export a series of images into

// your default Downloads folder. These can then be made into an animated gif. 

// This code is known to work with p5.js version 0.6.0

// Prof. Golan Levin, 28 January 2018

​

// INSTRUCTIONS FOR EXPORTING FRAMES (from which to make a GIF): 

// 1. Run a local server, using instructions from here:

//    https://github.com/processing/p5.js/wiki/Local-server

// 2. Set the bEnableExport variable to true. DON'T FORGET!

// 3. Set the myNickname variable to your name.

// 4. Run the program from Chrome; press 'f'. Then, 

//    Look in your 'Downloads' folder for the generated frames.

// 5. Note: Retina screens may export frames at twice the resolution.

// 6. Compile the frames into a GIF using a tool like ezgif.com.

​

​

//===================================================

// User-modifiable global variables. 

var myNickname = "nickname";

var nFramesInLoop = 120;

var bEnableExport = true;

​

// Other global variables you don't need to touch.

var nElapsedFrames;

var bRecording;

var theCanvas;

​

//===================================================

function setup() {

  theCanvas = createCanvas(500, 200);

  bRecording = false;

  nElapsedFrames = 0;

}

​

//===================================================

function keyTyped() {

  if (bEnableExport) {

    if ((key === 'f') || (key === 'F')) {

      bRecording = true;

      frameRate(2); // while we're exporting

      nElapsedFrames = 0;

    }

  }

}

​

//===================================================

function draw() {

​

  // Compute a percentage (0...1) representing where we are in the loop.

  var percentCompleteFraction = 0;

  if (bRecording) {

    percentCompleteFraction = float(nElapsedFrames) / float(nFramesInLoop);

  } else {

    percentCompleteFraction = float(frameCount % nFramesInLoop) / float(nFramesInLoop);

  }

​

  // Render the design, based on that percentage. 

  // This function renderMyDesign() is the one for you to change. 

  renderMyDesign(percentCompleteFraction);

​

  // If we're recording the output, save the frame to a file. 

  // Note that the output images may be 2x large if you have a Retina mac. 

  // You can compile these frames into an animated GIF using a tool like: 

  if (bRecording && bEnableExport) {

    var frameOutputFilename = myNickname + "_frame_" + nf(nElapsedFrames, 4) + ".png";

    print("Saving output image: " + frameOutputFilename);

    // saveCanvas(theCanvas, frameOutputFilename, 'png');

    save(theCanvas, frameOutputFilename);

    nElapsedFrames++;

​

    if (nElapsedFrames >= nFramesInLoop) {

      bRecording = false;

      frameRate(60);

    }

  }

}

​

//===================================================

function renderMyDesign(percent) {

  //

  // THIS IS WHERE YOUR ART GOES. 

  // This is an example of a function that renders a temporally looping design. 

  // It takes a "percent", between 0 and 1, indicating where we are in the loop. 

  // Use, modify, or delete whatever you prefer from this example. 

  // This example uses several different graphical techniques. 

  // Remember to SKETCH FIRST!

​

  //----------------------

  // here, I set the background and some other graphical properties

  background(180);

  smooth();

  stroke(0, 0, 0);

  strokeWeight(2);

​

  //----------------------

  // Here, I assign some handy variables. 

  var cx = 100;

  var cy = 100;

​

  //----------------------

  // Here, I use trigonometry to render a rotating element.

  var radius = 80;

  var rotatingArmAngle = percent * TWO_PI;

  var px = cx + radius * cos(rotatingArmAngle);

  var py = cy + radius * sin(rotatingArmAngle);

  fill(255);

  line(cx, cy, px, py);

  ellipse(px, py, 20, 20);

​

  //----------------------

  // Here, I use graphical transformations to render a rotated square. 

  // Notice the use of push(), pop(), translate(), etc. 

  push();

  translate(cx, cy);

  var rotatingSquareAngle = percent * TWO_PI * -0.25;

  rotate(rotatingSquareAngle);

  fill(255, 128);

  rect(-40, -40, 80, 80);

  pop();

​

  //----------------------

  // Here's a linearly-moving square

  var squareSize = 20;

  var topY = 0 - squareSize - 2;

  var botY = height + 2;

  var sPercent = (percent + 0.5) % 1.0; // shifted by a half-loop

  var yPosition = map(sPercent, 0, 1, topY, botY);

  fill(255, 255, 255);

  rect(230, yPosition, 20, 20);

​

  //----------------------

  // Here's a sigmoidally-moving pink square!

  // This uses the "Double-Exponential Sigmoid" easing function 

  // ripped from From: https://idmnyu.github.io/p5.js-func/

  // Really, you should just include this library!!

  var eased = doubleExponentialSigmoid(percent, 0.7);

  eased = (eased + 0.5) % 1.0; // shifted by a half-loop, for fun

  var yPosition2 = map(eased, 0, 1, topY, botY);

  fill(255, 200, 200);

  rect(260, yPosition2, 20, 20);

​

  //----------------------

  // Here's a pulsating ellipse

  var ellipsePulse = sin(3.0 * percent * TWO_PI);

  var ellipseW = map(ellipsePulse, -1, 1, 20, 50);

  var ellipseH = map(ellipsePulse, -1, 1, 50, 30);

  var ellipseColor = map(ellipsePulse, -1, 1, 128, 255);

  fill(255, ellipseColor, ellipseColor);

  ellipse(350, cy, ellipseW, ellipseH);

​

  //----------------------

  // Here's a traveling sine wave

  stroke(0, 0, 0);

  for (var sy = 0; sy <= height; sy += 4) {

    var t = map(sy, 0, height, 0.0, 0.25);

    var sx = 450 + 25.0 * sin((t + percent) * TWO_PI);

    ellipse(sx, sy, 1, 1);

  }

​

  //----------------------

  // Include some visual feedback. 

  fill(255, 0, 0);

  noStroke();

  textAlign(CENTER);

  var percentDisplayString = "" + nf(percent, 1, 3);

  text(percentDisplayString, cx, cy - 15);

}

​

​

// Symmetric double-element sigmoid function ('_a' is the slope)

// See https://github.com/IDMNYU/p5.js-func/blob/master/lib/p5.func.js

// From: https://idmnyu.github.io/p5.js-func/

//===================================================

function doubleExponentialSigmoid(_x, _a) {

  if (!_a) _a = 0.75; // default

​

  var min_param_a = 0.0 + Number.EPSILON;

  var max_param_a = 1.0 - Number.EPSILON;

  _a = constrain(_a, min_param_a, max_param_a);

  _a = 1 - _a;

​

  var _y = 0;

  if (_x <= 0.5) {

    _y = (pow(2.0 * _x, 1.0 / _a)) / 2.0;

  } else {

    _y = 1.0 - (pow(2.0 * (1.0 - _x), 1.0 / _a)) / 2.0;

  }

  return (_y);

}