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About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

     

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About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

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About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient. For instance, CoffeeScript can help prevent easy-to-make mistakes and offer a cleaner syntax and Babel can bring ECMAScript 6 features to browsers that only support ECMAScript 5.

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You're using npm packages, so we've auto-selected Babel for you here, which we require to process imports and make it all work. If you need to use a different JavaScript preprocessor, remove the packages in the npm tab.

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You can apply a script from anywhere on the web to your Pen. Just put a URL to it here and we'll add it, in the order you have them, before the JavaScript in the Pen itself.

If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.

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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

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HTML

            
              <header></header>

<section>
  <div><video src="" crossorigin="anonymous" autoplay></video></div>
  <canvas></canvas>
</section>

<footer>
  <p>
    This makes music and needs access to your camera.
    The average hue from your camera controls which chord will play.
  </p>
  <p><button id="button"><span>Start</span><span>Stop</span></button></p>
</footer>

<div class="trydebug hide">
  Bummer, you cant load this here. You can open
  <a href="https://codepen.io/jakealbaugh/debug/ZxLKvG" target="blank">
    this page
  </a> in a new window which might fix the problem.
</div>
!

CSS

            
              html, body {
  height: 100%;
  overflow: hidden;
}

body, section {
  background: #111;
}

$size: 300px;

div.trydebug {
  position: absolute;
  top: 50%;
  left: 50%;
  box-sizing: border-box;
  z-index: 10;
  padding: 4rem;
  width: 400px;
  max-width: 95%;
  transform: translate(-50%, -50%);
  background: black;
  color: white;
  text-align: center;
  border: 2px solid tomato;
  a {
    color: tomato;
  }
  &.hide {
    display: none;
  }
}

section {
  height: $size * 2;
  width: $size;
  position: absolute;
  left: calc(50% - #{$size * 0.5});
  top: calc(50% - #{$size});
  flex-direction: column;
  display: flex;
  box-shadow: 0px 4px 24px 4px rgba(0, 0, 0, 0.1);
  border-radius: 4px;
  overflow: hidden;
  div, canvas {
    height: $size;
    width: $size;
    display: block;
  }
  div {
    overflow: hidden;
    position: relative;
    video {
      display: block;
      position: absolute;
      top: 0;
      left: 50%;
      transform: translateX(-50%);
      width: auto;
      height: 100%;
    }
  }

  canvas {
    image-rendering: pixelated;
  }
}


header {
  position: fixed;
  font-family: system, Helvetica, Arial, sans-serif;
  color: white;
  width: $size;
  left: calc(50% - #{$size * 0.5});
  top: calc(50% + #{$size + 10});
  display: flex;
  > div {
    flex: 1;
    height: 20px;
    position: relative;
    display: flex;
    border-radius: 4px;
    box-shadow: 0px 4px 24px 4px rgba(0, 0, 0, 0.1);
    overflow: hidden;
    > span {
      flex: 1;
    }
    > span:last-child {
      position: absolute;
      display: block;
      top: 0;
      width: 2px;
      height: 20px;
      background: white;
      transform: translateX(-50%);
    }
  }
}

footer {
  position: absolute;
  bottom: 0;
  left: 50%;
  box-sizing: border-box;
  width: 100%;
  padding: 12px;
  text-align: center;
  transform: translateX(-50%);
  max-width: $size * 2;
  color: white;
  text-shadow: 2px 2px 0px rgba(0,0,0,0.2);
  -webkit-font-smoothing: antialiased;
	-moz-osx-font-smoothing: grayscale;
  button {
    appearance: none;
    border: none;
    padding: 12px 24px;
    border-radius: 4px;
    box-shadow: 0px 2px 0px 1px rgba(0, 0, 0, 0.3);
    background: black;
    color: white;
    cursor: pointer;
    font-size: 24px;
    // text-transform: uppercase;
    font-weight: bold;
    &.active {
      background: white;
      color: black;
    }
    &:active {
      box-shadow: 0px 0px 0px 1px rgba(0, 0, 0, 0.3);
      transform: translateY(2px);
    }
    &:not(.active) span:last-child,
    &.active span:first-child {
      display: none;
    }
  }
}

@media (min-width: #{$size * 2}) {
  section {
    width: $size * 2;
    height: $size;
    flex-direction: row;
    left: calc(50% - #{$size});
    top: calc(50% - #{$size * 0.5});
  }
  header {
    top: calc(50% + #{$size * 0.5 + 10});
    width: $size * 2;
    left: calc(50% - #{$size});
  }
}
!

JS

            
              // console.clear();

class ColorMapper {
  constructor(di, vid, cvs) {
    this.di = di;
    this.cvs = cvs;
    this.ctx = cvs.getContext('2d');
    this.vid = vid;
    this.rgb = new Array(di * di);
    this.report = document.querySelector('header');
    this.avgRGB = null;
    this.avgHSL = null;
    this._initialize();
  }

  start(stream) {
    try {
      this.vid.srcObject = stream;
    } catch (error) {
      console.log(error)
      this.vid.src = URL.createObjectURL(stream);
    }
    this.vid.play();
    let self = this;
    this.vid.onloadedmetadata = function() { 
      self.w = self.vid.videoWidth / self.vid.videoHeight * self.cvs.width;
      self.vid.width = self.vid.videoWidth;
      self.vid.height = self.vid.videoHeight;
      self.offX = (self.w - self.cvs.width) * -0.5;
      self._animate();
    }
  }

  _animate() {
    window.requestAnimationFrame(this._animate.bind(this));
    this.ctx.drawImage(this.vid, this.offX, 0, this.w, this.di);
    this._processData();
  }
  
  _initialize() {
    this.cvs.height = this.di;
    this.cvs.width  = this.di;
  }
  
  _processData() {
    let imgData = this.ctx.getImageData(0, 0, this.di, this.di),
        data = imgData.data,
        len = data.length,
        avg = [0, 0, 0];
    for (let i = 0; i < len; i += 4) {
      let colorIdx = i * 0.25,
        newRgb = [data[i], data[i + 1], data[i + 2]],
        prevRgb = this.rgb[colorIdx],
        easeRgb = this._easeVals(prevRgb, newRgb);
      imgData.data[i + 0] = easeRgb[0];
      imgData.data[i + 1] = easeRgb[1];
      imgData.data[i + 2] = easeRgb[2];
      avg[0] += easeRgb[0];
      avg[1] += easeRgb[1];
      avg[2] += easeRgb[2];
      this.rgb[colorIdx] = easeRgb;
    }
    let colors = len * 0.25;
    avg[0] /= colors;
    avg[1] /= colors;
    avg[2] /= colors;
    this.avgRGB = avg;
    this.avgHSL = this._rgbToHsl(avg);
    document.body.style.backgroundColor = `rgb(${avg.map(Math.round).join(',')})`;
    this.ctx.putImageData(imgData, 0, 0);
    this.report.innerHTML = `
      ${this._gradientSpan('h', this.avgHSL[0])}
    `
  }
  
  _gradientSpan(type, value) {
    let gradient = [];
    
    if (type === 'h')
      for (let i = 0; i < 7; i++)
        gradient.push(`hsl(${i / 7 * 360}, 100%, 60%)`);
    else if (type === 's')
      for (let i = 0; i < 7; i++)
        gradient.push(`hsl(0, ${i / 7 * 100}%, 60%)`);
    else if (type === 'l')
      for (let i = 0; i < 7; i++)
        gradient.push(`hsl(0, 0%, ${i / 7 * 100}%)`);
    return `
      <div>
        ${gradient.map(g => `<span style="background-color: ${g}"></span>` ).join('')}
        <span style="left: ${value * 100}%"></span>
      </div>
    `;
  }
  
  _easeVals(prev, next, ease = 0.025) {
    if (!prev) return next;
    return next.map((n, i) => (n - prev[i]) * ease + prev[i]);
  }

  // https://stackoverflow.com/questions/2353211/hsl-to-rgb-color-conversion
  _rgbToHsl(rgb) {
    let [r, g, b] = rgb;
    r /= 255, g /= 255, b /= 255;
    let max = Math.max(r, g, b), min = Math.min(r, g, b);
    let h, s, l = (max + min) / 2;

    if (max == min) h = s = 0;
    else {
      let d = max - min;
      s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
      switch (max) {
        case r: h = (g - b) / d + (g < b ? 6 : 0); break;
        case g: h = (b - r) / d + 2; break;
        case b: h = (r - g) / d + 4; break;
      }
      h /= 6;
    }

    return [h, s, l];
  }
}

class Score {
  constructor(map) {
    this.map = map;
    this.noteIdx = 0;
    this.tick = 0;
    this._initialize();
  }
  
  toggle() {
    if (this.on) {
      this.on = false;
      Tone.Transport.stop();
      this.tick = 0;
      this.synth.triggerRelease();
      this.mid.triggerRelease();
      this.bass1.triggerRelease();
      this.bass2.triggerRelease();
      document.querySelector('button').classList.remove('active');
    } else {
      this.on = true;
      Tone.Transport.start();
      document.querySelector('button').classList.add('active');
    }
  }

  step(time) {
    let hsl = this.map.avgHSL,
      safe = i => Math.max(0, i - 0.000000001);
    if (!hsl || !this.on) return;
    if (this.tick % 4 === 0) {
      this.noteIdx = Math.floor(safe(hsl[0]) * 7);
      this.hsl = hsl;
    }
    let note = this.note,
      pattern = [2, 0, 1, 0, 2, 1, 2, 0],
      octaves = [5, 5, 4, 4, 4, 5, 4, 4],
      arpNote = note[pattern[this.tick % 8]],
      arpOct = octaves[this.tick % 8];
    arpOct += arpNote[1];
    let arp = `${arpNote[0]}${arpOct}`;
    let mtd = (this.tick === 0) ? 'triggerAttack' : 'setNote';
    this.synth[mtd](arp, time);
    if (this.tick % 4 === 0) {
      let bass1 = note[0],
        bass2 = note[2],
        mid = note[1];
      this.mid[mtd](mid[0]+(mid[1]+3), time);
      this.bass1[mtd](bass1[0]+(bass1[1]+1), time);
      this.bass2[mtd](bass2[0]+(bass2[1]+1), time);
    }
    this.tick++;
  }

  get note() {
    return this.notes[this.noteIdx];
  }
  
  get notes() {
    return [
      [['G',  0], ['A#', 0], ['C#', 1]],
      [['A#', 0], ['C#', 1], ['F',  1]],
      [['C#', 1], ['F',  1], ['G#', 1]],
      [['F',  1], ['G#', 1], ['C',  2]],
      [['D#', 1], ['G',  1], ['A#', 1]],
      [['C',  1], ['D#', 1], ['G',  1]],
      [['G#', 0], ['C',  1], ['D#', 1]],
    ];
    // return [
    //   [['G',  0], ['A#', 0], ['C#', 1]],
    //   [['G#', 0], ['C',  1], ['D#', 1]],
    //   [['A#', 0], ['C#', 1], ['F',  1]],
    //   [['C',  1], ['D#', 1], ['G',  1]],
    //   [['C#', 1], ['F',  1], ['G#', 1]],
    //   [['D#', 1], ['G',  1], ['A#', 1]],
    //   [['F',  1], ['G#', 1], ['C',  2]],
    // ];
  }
  
  _initialize() {
    this.synth = new Tone.Synth({
      portamento: 0.00625,
      oscillator: { type: 'sine' },
      envelope: { release: 0.07 }
    });
    this.mid = new Tone.Synth({
      portamento: 0.00625,
      oscillator: { type: 'triangle' },
      envelope: { release: 0.07 }
    });
    this.bass1 = new Tone.FMSynth({
      portamento: 0.0125
    });
    this.bass2 = new Tone.FMSynth({
      portamento: 0.0125
    });
    let gain1 = new Tone.Gain(0.4),
      gain2 = new Tone.Gain(0.5),
      pan1 = new Tone.Panner(-1),
      pan2 = new Tone.Panner(1);
    this.synth.connect(gain1);
    this.mid.connect(gain1);
    pan1.connect(gain2);
    pan2.connect(gain2);
    this.bass1.connect(pan1);
    this.bass2.connect(pan2);
    gain1.toMaster();
    gain2.toMaster();
    Tone.Transport.scheduleRepeat(time => {
      this.step(time);
    }, '16n');
    Tone.Transport.bpm.value = 120;
  }
}

const vid = document.querySelector('video'),
  cvs = document.querySelector('canvas'),
  map = new ColorMapper(4, vid, cvs),
  score = new Score(map);

navigator.mediaDevices.getUserMedia({ audio: false, video: true })
  .then(stream => {
    map.start(stream);
    document.querySelector('button').addEventListener('click', () => score.toggle());
  })
  .catch(err => {
    if (window.location.href.match('debug')) {
      alert('Sorry. This wont work on your browser or device. Update or use Chrome/Firefox.')
    } else {
      document.querySelector('div.trydebug').classList.remove('hide');
    }
  });


StartAudioContext(Tone.context, '#button')
!
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