createJS caching tilemap background does not render - html

Question

If I don't cache the container of tiles after creating the map, I can see them rendered to the canvas:
function createWorld() {
background = new createjs.Container();
for (var y = 0; y < mapWidth; y++) {
for (var x = 0; x < mapHeight; x++) {
var tile = new createjs.Bitmap('images/tile.png');
tile.x = x * 28;
tile.y = y * 30;
background.addChild(tile);
}
}
//background.cache(0, 0, mapWidth, mapHeight);
stage.addChild(background);
}
If I do cache the background container of tile children, it won't render
function createWorld() {
background = new createjs.Container();
for (var y = 0; y < mapWidth; y++) {
for (var x = 0; x < mapHeight; x++) {
var tile = new createjs.Bitmap('images/tile.png');
tile.x = x * 28;
tile.y = y * 30;
background.addChild(tile);
}
}
background.cache(0, 0, mapWidth, mapHeight);
stage.addChild(background);
}
Why?

Answer 1

This is probably because that even when preloaded, images may not be available synchronously if you use a path to create them. If you aren't caching them, then they wouldn't show up immediately when the stage is updated -- but if you ticked the stage, they might appear to load instantly (they just take a frame or so).
I recommend you preload them, either internally, or using something like PreloadJS. Then pass the loaded instance to the bitmaps instead.
var img = document.createElement("img");
img.onload = draw;
img.src = "images/tile.png";
function draw() {
// loop
var bmp = new createjs.Bitmap(img); // Use a reference instead of a path
}
Note that this also reduces overhead, since only one image is created, and all the Bitmaps share a reference to it.
If all your tiles are the same, you might want to look at the Graphics.beginBitmapFill() method. http://www.createjs.com/Docs/EaselJS/classes/Graphics.html#method_beginBitmapFill