Cache SpriteSheets in EaselJS

问题

How can I cache SpriteSheets in EaselJS? I have a Sprite object and when I use user.hero.cache(0, 0, 30, 40); it stops playing animation (probably because I'm just caching the current frame, not the entire SpriteSheet image). So how can I cache it?

Here's my relevant EaselJS code:

data = {
    images: ["Graphics/hero.png"],
    frames: {
        width: 30,
        height: 40
    },
    animations: {
        stand: 0,
        run: [1, 2, "runLoop", 0.15],
        runLoop: [3, 7, true, 0.15],
        jump: [8, 10, "happy", 0.5],
        happy: 11,
        fall: 12,
        stopFalling: [13, 14, "stand", 0.2],
        almostFalling: [16, 19, true, 0.1]
    }
};
user.hero.spriteSheet = new createjs.SpriteSheet(data);
user.hero = new createjs.Sprite(user.hero.spriteSheet, "stand");
user.hero.name = "hero";
user.hero.x = user.hero.safeX = 40 * 3;
user.hero.y = user.hero.safeY = 0;
user.hero.offset = 4;
user.hero.regX = user.hero.offset + 2;
user.hero.regY = user.hero.offset;
user.hero.width = 30 - (user.hero.offset * 2) - 10;
user.hero.height = 40 - (user.hero.offset * 2);
user.hero.xvel = user.hero.yvel = 0;
user.hero.cache(0, 0, 30, 40); // <--- This is the problem.
movableObjContainer.addChild(user.hero);
movableObj.push(user.hero);

Without cache:

With cache:

I've tried caching the data.image or user.hero.spriteSheet too, without success. Is there any way to cache the SpriteSheet without compromising its animations?

回答1:

When you cache the sprite, you are saving off how it looks at that instant.

Can you explain why you want to cache it? The only reason I can think of to cache it would be to apply filters. Each time you cache it, the contents are drawn to an off-screen canvas, which is then drawn in place of it. This makes a lot of sense if you have complex content, like a container or graphics, which do not change, but with the spritesheet, it means you are creating a new bitmap to draw a bitmap. The spritesheet itself is a great way to be filesize, network, and GPU-optimzed, so re-caching it is basically negating all those benefits.

If you want to cache anyways, you will need to re-cache it, or call updateCache() every time it changes. Here is an example using the ticker.

createjs.Ticker.on("tick", function() {
    user.hero.updateCache();
    // or
    user.hero.cache(0,0,30,40) 
}, this);

Here is a quick demo I did a while back using a few approaches for filters. It provides an example of constant re-caching, as well as an example where the entire spritesheet is cached to apply the filter once, and then that cached version is used for the sprite. http://jsfiddle.net/lannymcnie/NRH5X/

来源：https://stackoverflow.com/questions/24499486/cache-spritesheets-in-easeljs