From 25fec83f6f7db468721a38adb2c84a0c0a2121f1 Mon Sep 17 00:00:00 2001
From: Jules Laplace <julescarbon@gmail.com>
Date: Tue, 6 Mar 2018 13:28:12 +0100
Subject: displaying waveform and spectrogram

---
 client/draw.js | 197 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 197 insertions(+)
 create mode 100644 client/draw.js

(limited to 'client/draw.js')

diff --git a/client/draw.js b/client/draw.js
new file mode 100644
index 0000000..a9c182d
--- /dev/null
+++ b/client/draw.js
@@ -0,0 +1,197 @@
+import {
+  browser, requestAudioContext,
+  randint, randrange, clamp,
+} from './lib/util'
+
+import mouse from './lib/mouse'
+import color from './lib/color'
+
+let w, h
+let rx, ry
+
+const canvas = document.createElement('canvas')
+const ctx = canvas.getContext('2d')
+
+document.body.appendChild(canvas)
+document.body.addEventListener('resize', resize)
+resize()
+recenter()
+requestAnimationFrame(animate)
+
+function resize(){
+  w = canvas.width = window.innerWidth
+  h = canvas.height = window.innerHeight
+  clear()
+}
+function recenter(){
+  rx = randint(w), ry = randint(h)
+}
+function animate(t){
+  requestAnimationFrame(animate)
+  ctx.save()
+  ctx.globalAlpha = 0.0001
+  ctx.translate(w/2, h/2)
+  ctx.rotate(0.1)
+  ctx.translate(-rx, -ry)
+  ctx.drawImage(canvas, 0, 0)
+  ctx.restore()
+}
+function clear(n, x, y, ww, hh){
+  ctx.fillStyle = 'rgba(255,255,255,' + (n || 0.5) + ')'
+  ctx.fillRect(x || 0, y || 0, ww || w, hh || h)
+  recenter()
+}
+function triangle(px,py,r){
+  setTimeout( () => tri(px,py,r), Math.random()*10)
+  // setTimeout( () => tri(px,py,r), Math.random()*200)
+  // setTimeout( () => tri(px,py,r), Math.random()*300)
+}
+function tri(px, py, r) {
+  ctx.save()
+  ctx.globalCompositeOperation = 'multiply'
+  ctx.fillStyle = color((px+py)/(w+h), 0, 1, 1)
+  function p(){
+    let theta = randrange(0, Math.PI*2)
+    let x = px + Math.cos(theta) * r
+    let y = py + Math.sin(theta) * r
+    return { x, y }
+  }
+  ctx.beginPath()
+  const p0 = p(), p1 = p(), p2 = p()
+  ctx.moveTo(p0.x, p0.y)
+  ctx.lineTo(p1.x, p1.y)
+  ctx.lineTo(p2.x, p2.y)
+  ctx.lineTo(p0.x, p0.y)
+  ctx.fill()
+  ctx.restore()
+}
+function line(y){
+  ctx.beginPath()
+  ctx.moveTo(0, y)
+  ctx.lineTo(w, y)
+  ctx.strokeStyle = "#888"
+  ctx.strokeWidth = 1
+  ctx.stroke()
+}
+function dot(x, y, r){
+  ctx.fillStyle = "#f00"
+  ctx.beginPath()
+  ctx.moveTo(x, y)
+  ctx.arc(x, y, r, 0, 2*Math.PI)
+  ctx.fill()
+}
+function waveform(pcm, sr, pos, zoom){
+  sr = sr || 44100
+  pos = pos || 0
+
+  var width = w
+  var height = Math.floor(h/4)
+  var half_height = Math.floor(height/2)
+  var x0 = 0
+  var y0 = 20
+  var ymid = y0 + half_height
+  var pixels_per_second = 1024
+  var max_width_in_seconds = width / pixels_per_second
+  var max_width_in_samples = max_width_in_seconds * sr
+  var pcm_length = pcm.length
+  var len = Math.min(pcm_length, max_width_in_samples)
+  var pcm_step = sr / pixels_per_second
+  var i
+  ctx.save()
+
+  clear(1, x0, y0, width, height)
+
+  line(ymid)
+  ctx.beginPath()
+  for (i = 0; i < width; i += 0.5) {
+    var si = Math.floor(pcm_step * i + pos)
+    if (si > pcm_length) break
+    var val = pcm[si] // -1, 1
+    // ctx.moveTo(x0 + i, ymid)
+    ctx.lineTo(x0 + i, ymid + val * half_height)
+  }
+  ctx.strokeStyle = "rgba(250,20,0,0.9)"
+  ctx.strokeWidth = 1
+  ctx.stroke()
+  ctx.restore()
+}
+
+const signalWindows = require('signal-windows').windows
+const FFTJS = require('fft.js')
+const fft_size = 1024
+const fft = new FFTJS(fft_size)
+
+function toSpectrum(pcm){
+  const ham = signalWindows.construct('ham', fft_size)
+  const pcm_in = new Array(fft_size)
+  const pcm_length = pcm.length
+  const pcm_q_length = Math.ceil(pcm_length / fft_size) * fft_size
+
+  let i, j, fft_out, spec = [];
+  for (i = 0; i < pcm_q_length; i += fft_size/4) {
+    for (j = 0; j < fft_size; j++) {
+      pcm_in[j] = pcm[i+j] * ham[j] || 0
+    }
+    fft_out = fft.createComplexArray()
+    fft.realTransform(fft_out, pcm_in)
+    spec.push(fft_out)
+  }
+
+  return spec
+}
+function spectrum(pcm, sr){
+  sr = sr || 44100
+  const spec = toSpectrum(pcm)
+
+  ctx.save()
+
+  const scratch = document.createElement('canvas')
+  scratch.width = spec.length
+  scratch.height = fft_size
+  const scratchCtx = scratch.getContext('2d')
+
+  var imageData = ctx.createImageData(scratch.width, scratch.height)
+  var data = imageData.data
+
+  let i, j, u, v, _r, _i, col, spec_len = spec.length
+  for (i = 0; i < spec_len; i++) {
+    col = spec[i]
+    for (j = 0; j < fft_size; j++) {
+      u = (j * spec_len + i) * 4
+      v = j * 2
+      _r = col[v]
+      _i = col[v+1]
+      // red - real part
+      data[u] = _r * 127 + 127
+      // green - imag part
+      data[u+1] = _i * 127 + 127
+      // blue - magnitude
+      data[u+2] = Math.sqrt(Math.pow(_r, 2) + Math.pow(_i, 2)) * 128 + 127
+      // data[u] = 128
+      // data[u+1] = 128
+      data[u+2] = 128
+      data[u+3] = 255
+    }
+  }
+
+  scratchCtx.putImageData(imageData, 0, 0)
+
+  var pcm_length = pcm.length
+  var pixels_per_second = 1024
+
+  const width = Math.round(pcm_length / sr * pixels_per_second) // ok not really this
+  const height = Math.floor(h*3/4)
+
+  const x0 = 0
+  const y0 = Math.floor(h/4) + 20
+  clear(1, x0, y0, w, height)
+  ctx.drawImage(scratch, x0, y0, width, height)
+
+  ctx.restore()
+}
+
+export default {
+  canvas, ctx,
+  triangle, clear, line, dot,
+  waveform, spectrum
+}
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-- 
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