Created
February 2, 2012 18:07
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Lightweight canvas wrapper.
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// Basic Usage: | |
// | |
// var main = new Canvas({ elem: "canvas" }, function(options) { | |
// // Instantiate anything specific here... | |
// // Main draw loop | |
// this.draw = function() { | |
// | |
// }; | |
// }); | |
// | |
// Canvas | |
function Canvas(opts, initialize) { | |
// Used to cache user defined draw method | |
var drawCache; | |
var drawObj = { now: +new Date, last: +new Date }; | |
// Set defaults | |
this.width = opts.width || 320; | |
this.height = opts.height || 240; | |
this.fps = opts.fps || 30; | |
// Query the DOM for canvas element using a selector | |
if (opts.canvas && typeof opts.canvas == "string") { | |
this.canvas = document.querySelector(opts.canvas); | |
// Set to element || undefined | |
} else { | |
this.canvas = opts.canvas; | |
} | |
// Initialize with the options | |
initialize.call(this, opts); | |
// Set the width/height on the canvas element | |
this.canvas.width = this.width; | |
this.canvas.height = this.height; | |
// Set the 2d context | |
this.ctx = this.canvas.getContext("2d"); | |
// Set correct fps | |
this.fps = 1000 / this.fps; | |
// Set to nop if user does not provide a function | |
drawCache = this.draw || function() {}; | |
// Wrap draw method | |
this.draw = function() { | |
var canvas = this; | |
drawObj.now = +new Date; | |
drawCache.call(canvas, drawObj); | |
// Set draw loop | |
window.setTimeout(function() { | |
requestAnimFrame(canvas.draw); | |
}, canvas.fps); | |
}.bind(this); | |
} | |
// Draw methods | |
Canvas.prototype = { | |
G: 6.673e-1, | |
clear: function() { | |
this.rect(0, 0, this.width, this.height); | |
}, | |
start: function() { | |
this.clear(); | |
this.draw(); | |
}, | |
rect: function(x, y, width, height) { | |
this.ctx.fillRect(x, y, width, height); | |
}, | |
line: function(px, py, x, y) { | |
this.ctx.beginPath(); | |
this.ctx.moveTo(px, py); | |
this.ctx.lineTo(x, y); | |
this.ctx.closePath(); | |
this.ctx.fill(); | |
this.ctx.stroke(); | |
}, | |
circle: function(x, y, radius) { | |
this.ctx.beginPath(); | |
this.ctx.arc(x, y, radius, 0, Math.PI * 2, true); | |
this.ctx.closePath(); | |
this.ctx.fill(); | |
}, | |
distance: function(x2, x1, y2, y1) { | |
return Math.sqrt(Math.pow(x2-x1, 2) + Math.pow(y2-y1, 2)); | |
}, | |
angleFromPoints: function(x1, x2, y1, y2) { | |
return Math.atan2(y2-y1, x2-x1); | |
}, | |
random: function(min, max, decimal) { | |
if (decimal) { | |
return Math.random() * (max - min) + min; | |
} | |
return Math.floor(Math.random() * (max - min+1)) + min; | |
} | |
}; |
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