rpi-ws281x-canvas

control ws281x-LEDs using a html5-canvas in node.js

this package allows you to control a grid of WS281x-LEDs (like the Adafruit Neopixel) using a canvas-element in node.js. This package provides a small wrapper around the node-canvas-module which mainly handles the format-conversion from canvas pixel-data to the Uint32-format required by the rpi-ws281x-native-module.

Setup

install via npm:

npm install rpi-ws281x-canvas

or from source:

git clone https://github.com/raspberry-node/node-rpi-ws281x-canvas.git
cd node-rpi-ws281x-canvas
npm install

Usage

The module exports a create(width, height)-function that will return an instance of a Canvas-element.

var ws281xCanvas = require('rpi-ws281x-canvas'),
    canvas = ws281xCanvas.create(10,10);

The returned is an instance of a HTML5-Canvas implementation (node-canvas).

The only additional method - toUint32Array() - handles the conversion of canvas pixel-data into the data-format used by the rpi-ws281x-native-module (unsigned 32-bit integer per pixel, format: 0x00rrggbb). For conversion of alpha-values, a black background is assumed.

In Addition to that there are two classes, Image and Font, that are made available as additional exports of the module.

Example

This will draw a blue rectangle on the LED-Grid.

var ws281x = require('rpi-ws281x-native'),
    canvas = require('rpi-ws281x-canvas').create(10,10),
    ctx = canvas.getContext('2d');

ws281x.init(100);

ctx.fillStyle = 'blue';
ctx.fillRect(2, 2, 8, 8);

ws281x.render(canvas.toUint32Array());

Testing

a simple test-script is provided in examples/sprite-animation.js, it is intended to run with a 10x10 matrix, so you might need to adjust the values to match your setup.