canvio

Simple JS canvas library

canvio is intended to address the problem that the Canvas API is less than simple, and not particularly intuitive. I wanted to be able to have the canvas just do something when I asked it to, instead of requiring 23 other calls along with it.

I may exaggerate. Slightly.

Basic Functionality

Images

The canvio.Image type provides functionality for using or generating images on the canvas.

Retrieving and displaying an external image:

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

var img = new canvio.Image();
img.init(ctx, 600, 300);
img.setSource("https://placehold.it/600x300");

Generating an image based on RGBA patterns:

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

var img = new canvio.Image();
img.init(ctx, 600, 600);

function red(x, y) {
  return 255 * Math.sin(x);
}

function green(x, y) {
  return 255 * Math.cos(x);
}

function blue(x, y) {
  return 255 * Math.sin(x + y);
}

function alpha(x, y) {
  return 255;
}

img.setPattern(red, green, blue, alpha);

Turtle

The canvio.Turtle class is a mimic of Python's turtle functionality. The analogy is that you have a pen (a "turtle") which starts at the center of the canvas, and which you can give instructions like forward(100), left(45), and so on.

Drawing a square:

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

var t = new canvio.Turtle(ctx);

for (var i = 0; i < 4; i++) {
  t.forward(100);
  t.right(90);
}

Drawing a circle:

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

var t = new canvio.Turtle(ctx);

for (var i = 0; i < 360; i++) {
  t.forward(1);
  t.right(1);
}

Canvas API

There's also a simplified version of the Canvas API in canvio, which enables you to perform basic canvas operations in a much simpler fashion.