Sparkline

A Web-Assembly sparkline (mini-chart) control written in C and TypeScript. Designed to be fast.

Installation

npm i -S @guidestar/sparkline

Performance

Using web assembly to write the pixels directly, this control can render 1 million audio samples in roughly 15 milliseconds on my Macbook Air M1.

Run the demo and open your console to see it live.

Demo: Waveform / Oscillogram)

The demo application code can be found in demos/sparkline.

Run the demo:

cd demos/sparkline
npm run demo

Grant website access to your microphone and then click "Start Recording..." Two oscillograms will demonstrate rendering to canvases.

Example (Basic)

import Sparkline from '@guidestar/sparkline'

// Note: You need to get a HTML <canvas> instance at some point here before
// calling renderWave.

...

const width = 500;
const height = 200;

const data = [];
for (let i = 0; i < 10000; i++) data[i] = Math.random()

const sparkline = new Sparkline({
  ready: () => {
    sparkline.renderWaveForm(canvas, data, width, height, {
      backgroundColor: 0xFFCCAA88,   // Colors are 0x[ALPHA][BLUE][GREEN][RED]
      foregroundColor: 0xFFAAAAAA,
      fillBackground: true
    });
  }
});

Example (Ticks)

You can render ticks every X milliseconds rather easily, with custom colors:

import Sparkline from '@guidestar/sparkline'

const data = [...]; // Get an array with lots of numbers...

const sampleRate = 8000; // This is the sample rate of your audio, in samples per second.

let sparklineReady = false;

const sparkline = new Sparkline({
  ready: () => sparklineReady = true
});

...

if (sparklineReady) {
  sparkline.renderWaveForm(canvas, data, width, height, {
    backgroundColor: 0xFFCC4444,
    foregroundColor: 0xFFFFFFFF,
    sampleRate, // required to know where to mark the ticks
    verticalTicks: [{
      ms: 100, // A medium grey tick every 100 milliseconds
      height: 10,
      color: 0xFF888888
    }, {
      ms: 1000, // A lighter grey tick every 1 second
      height: 20,
      color: 0xFFCCCCCC
    }]
  });
}

Development

You will need to install Emscripten and ensure that emcc is available on your path.

Once that is done, you can cd into the /sparkline directory (NOT the demo directory) and:

npm run dev

This will startup a really rudimentary chokidar watching the sparkline directory and rebuilding whenever it sees a change in the .c or .ts files.

It then starts a mini web-server at localhost:8080 where you can see a demo of the audio wave-form working.

Build

Building involves compiling the C code to WASM, which is then base-64d and built into a webpack bundled Javascript file. You can see the final file in dist/sparkline.js.

npm run build

License

The MIT License (MIT)

Copyright (c) 2023 Joshua Jung

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.