canvas-to-pixels

Convert canvas actions into pixels

This is part of the gifsockets project. It is an alternative engine to the default phantomjs-pixel-server.

Getting Started

This module depends on node-canvas. Please satisfy its dependencies before using.

Documentation here: https://github.com/LearnBoost/node-canvas/wiki

Install the module with: npm install canvas-to-pixels

var canvasToPixels = require('canvas-to-pixels');
canvasToPixels({
  width: 10,
  height: 10,
  js: (canvas, cb) {
    var context = canvas.getContext('2d');
    context.fillStyle = '#BADA55';
    context.fillRect(0, 0, 10, 10);
    cb();
  }
}, function receivePixels (err, pixels) {
  // pixels is [186,218,85,255,186,218, ..., 255]
});

Documentation

canvas-to-pixels returns canvasToPixels as its module.exports

canvasToPixels(options, cb)

Run JavaScript function against canvas receive call back with PixelArray

• options Object
  • width Number - Width of canvas and output image
  • height Number - Height of canvas and output image
  • js Object - Container for commands to run against a canvas instance
    • This can be prepared by passing a function to [function-to-string][]
    • The function itself should have a signature of function (canvas, cb) {}
    • params String[] - Array of parameter names for a function
      • The first parameter will be a canvas instance with the provided width and height
    • body String - Body of the function to execute
      • This must callback when it is completed (second parameter)
      • It is expected that js.body will write out the content you want to the canvas
• cb Function - Error-first callback that will receive PixelArray
  • Function signature should be function (err, pixels) {}
  • err Error - An error if any occurred while generating pixels
  • pixels PixelArray - An rgba array of pixels values from the canvas
    • PixelArrays behave just like normal arrays except they lack methods like concat
    • An rgba array is an array that contains subsequences of length 4 representing the red, green, blue, and alpha values for a pixel.
      • For example, [0, 1, 2, 3, 4, 5, 6, 7] is 2 pixels with r: 0, g: 1, b: 2, a: 3 and r: 4, g: 5, b: 6, a: 7
      • Each value can range from 0 to 255
    • If you would like to coerce pixels into a normal array, run

var normalArray = Array.prototype.slice.call(pixels);

Donating

Support this project and others by twolfson via gittip.

Contributing

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint via grunt and test via npm test.

Unlicense

As of Nov 15 2013, Todd Wolfson has released this repository and its contents to the public domain.

It has been released under the UNLICENSE.