Всем привет, пытаюсь разобраться в уроке
// Copyright 2013 William Malone ([url]www.williammalone.com[/url])
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// [url]http://www.apache.org/licenses/LICENSE-2.0[/url]
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
(function() {
// [url]http://paulirish.com/2011/requestanimationframe-for-smart-animating/[/url]
// [url]http://my.opera.com/emoller/blog/2011/12/20/requestanimationframe-for-smart-er-animating[/url]
// requestAnimationFrame polyfill by Erik Möller. fixes from Paul Irish and Tino Zijdel
// MIT license
var lastTime = 0;
var vendors = ['ms', 'moz', 'webkit', 'o'];
for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];
window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame']
|| window[vendors[x]+'CancelRequestAnimationFrame'];
}
if (!window.requestAnimationFrame)
window.requestAnimationFrame = function(callback, element) {
var currTime = new Date().getTime();
var timeToCall = Math.max(0, 16 - (currTime - lastTime));
var id = window.setTimeout(function() { callback(currTime + timeToCall); },
timeToCall);
lastTime = currTime + timeToCall;
return id;
};
if (!window.cancelAnimationFrame)
window.cancelAnimationFrame = function(id) {
clearTimeout(id);
};
}());
(function () {
var coin,
coinImage,
canvas;
function gameLoop () {
window.requestAnimationFrame(gameLoop);
coin.update();
coin.render();
}
function sprite (options) {
var that = {},
frameIndex = 0,
tickCount = 0,
ticksPerFrame = options.ticksPerFrame || 0,
numberOfFrames = options.numberOfFrames || 1;
that.context = options.context;
that.width = options.width;
that.height = options.height;
that.image = options.image;
that.update = function () {
tickCount += 1;
if (tickCount > ticksPerFrame) {
tickCount = 0;
// If the current frame index is in range
if (frameIndex < numberOfFrames - 1) {
// Go to the next frame
frameIndex += 1;
} else {
frameIndex = 1;
}
}
};
that.render = function () {
// Clear the canvas
that.context.clearRect(0, 0, that.width, that.height);
// Draw the animation
that.context.drawImage(
that.image,
frameIndex * that.width / numberOfFrames,
0,
that.width / numberOfFrames,
that.height,
0,
0,
that.width / numberOfFrames,
that.height);
};
return that;
}
// Get canvas
canvas = document.getElementById("coinAnimation");
canvas.width = 1200;
canvas.height = 128;
// Create sprite sheet
coinImage = new Image();
// Create sprite
coin = sprite({
context: canvas.getContext("2d"),
width: 640,
height: 128,
image: coinImage,
numberOfFrames: 5,
ticksPerFrame: 5
});
// Load sprite sheet
coinImage.addEventListener("load", gameLoop);
coinImage.src = "img/SpriteMen.png";
} ());
Со скоростью и кадрами понятно, но не понятно, как в таком случае задать первоначальное положение объекта sprite, подскажите пожалуйста, кто знает.
