atlases.js

var gSpriteSheets = {};

SpriteSheetClass = Class.extend({

	img: null,

	url: "",

	sprites: new Array(),

	init: function () {},

	load: function (imgName) {
        this.url = imgName;

	var img = new Image();
	img.src = imgName;
	this.img = img;

	gSpriteSheets[imgName] = this;
	},

	defSprite: function (name, x, y, w, h, cx, cy) {
	   var spt = {
		"id": name,
		"x": x,
		"y": y,
		"w": w,
		"h": h,
		"cx": cx == null ? 0 : cx,
		"cy": cy == null ? 0 : cy
	};

	this.sprites.push(spt);
	},

        parseAtlasDefinition: function (atlasJSON) {
        var parsedJSON = JSON.parse(atlasJSON);

        for (var key in parsedJSON.frames) {
           var sprite = parsedJSON.frames[key];
           var cx = -sprite.frame.w*0.5;
           var cy = -sprite.frame.h*0.5;
           this.defSprite(key, sprite.frame.x, sprite.frame.y, sprite.frame.w, sprite.frame.h, cx, cy);
      }   
	}
});