first commit

.gitignore

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+# Created by .ignore support plugin (hsz.mobi)
+### Example user template template
+### Example user template
+
+# IntelliJ project files
+.idea
+*.iml
+out
+gen
+node_modules/

index.js

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+module.exports = require('./lib/render')

lib/render.js

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+var AudioContext = require('web-audio-api').AudioContext;
+var fs = require('fs');
+var Canvas = require('canvas')
+
+Array.prototype.max = function () {
+  return Math.max.apply(null, this);
+};
+
+var defaultSetting = {
+  width: 600,
+  height: 80,
+  barWidth: 3,
+  barGap: 0.2,
+  waveColor: "blue",
+  waveAlpha: 1,
+  backgroundColor: '#fff',
+  baseline: 60,
+}
+
+function bufferMeasure(position, length, data) {
+  var sum = 0.0
+  for (var i = position; i <= (position + length) - 1; i++) {
+    sum += Math.pow(data[i], 2)
+  }
+  return Math.sqrt(sum / data.length)
+}
+
+module.exports = function render(url, options, cb) {
+  var audioContext = new AudioContext
+  if (typeof options === "function") {
+    cb = options
+    options = {}
+  }
+
+  options = Object.assign({}, defaultSetting, options)
+  if (options.baseline < 0 && options.height < 0 && options.width < 0) {
+    return cb( new Error('Size must be greater than 0'))
+  }
+
+  if (options.baseline > options.height) {
+    return cb( new Error('Baseline must be smaller than waveform height'))
+  }
+
+  var canvas = new Canvas(options.width, options.height)
+  var canvasContext = canvas.getContext('2d')
+
+  fs.readFile("Canon.mp3", function (err, buffer) {
+
+    if (err) {
+      return cb(err)
+    }
+
+    audioContext.decodeAudioData(buffer, function (result) {
+      var data = result.getChannelData(0)
+      var step = Math.floor(result.length / options.width)
+      var ratio = options.baseline / options.height
+      var vals = []
+
+      canvasContext.fillStyle = options.backgroundColor
+      canvasContext.fillRect(0, 0, options.width, options.height)
+
+      canvasContext.fillStyle = options.waveColor
+
+      for (var i = 0; i < options.width; i += options.barWidth) {
+        vals.push(bufferMeasure(i * step, step, data) * 10000);
+      }
+
+      for (var j = 0; j < options.width; j += options.barWidth) {
+        var scale = options.height / vals.max();
+        var val = bufferMeasure(j * step, step, data) * 10000;
+        val *= scale;
+        val += 1;
+        var w = options.barWidth;
+        if (options.barGap !== 0) {
+          w *= Math.abs(1 - options.barGap);
+        }
+        var x = j + (w / 2);
+
+        var lowerHeight = val * ratio;
+        var upperHeight = val * (1 - ratio);
+
+        if(options.waveAlpha < 1) {
+          canvasContext.clearRect(x, options.baseline, w, upperHeight);
+          canvasContext.clearRect(x, options.baseline, w, -lowerHeight);
+        }
+        canvasContext.fillRect(x, options.baseline, w, upperHeight);
+        canvasContext.fillRect(x, options.baseline, w, -lowerHeight);
+      }
+      cb(null, canvas.toBuffer())
+    })
+  });
+}

package.json

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+{
+  "name": "node-wave",
+  "version": "0.0.1",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "standard && node index.js"
+  },
+  "author": "Tran Quoc Cuong <[email protected]>",
+  "license": "MIT",
+  "dependencies": {
+    "canvas": "^1.6.2",
+    "web-audio-api": "^0.2.2"
+  },
+  "devDependencies": {
+    "standard": "^8.6.0"
+  }
+}

test/test.js

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+var render = require('../lib/render')
+var fs = require('fs')
+
+render('Canon.mp3', function (err, buffer) {
+  fs.writeFileSync('out.png', buffer);
+})