<!doctype html><html><head><meta charset="utf-8"><title>canvas爱心</title><style>html,body {height: 100%;padding: 0;margin: 0;background: #000;}canvas {position: absolute;width: 100%;height: 100%;}</style></head><body><canvas id="pinkboard"></canvas><script>/** Settings*/var settings = {particles: {length: 500, // maximum amount of particlesduration: 2, // particle duration in secvelocity: 100, // particle velocity in pixels/seceffect: -0.75, // play with this for a nice effectsize: 30, // particle size in pixels},};/** RequestAnimationFrame polyfill by Erik M?ller*/(function() {var b = 0;var c = ["ms", "moz", "webkit", "o"];for (var a = 0; a < c.length && !window.requestAnimationFrame; ++a) {window.requestAnimationFrame = window[c[a] + "RequestAnimationFrame"];window.cancelAnimationFrame = window[c[a] + "CancelAnimationFrame"] || window[c[a] +"CancelRequestAnimationFrame"]}if (!window.requestAnimationFrame) {window.requestAnimationFrame = function(h, e) {var d = new Date().getTime();var f = Math.max(0, 16 - (d - b));var g = window.setTimeout(function() {h(d + f)}, f);b = d + f;return g}}if (!window.cancelAnimationFrame) {window.cancelAnimationFrame = function(d) {clearTimeout(d)}}}());/** Point class*/var Point = (function() {function Point(x, y) {this.x = (typeof x !== 'undefined') ? x : 0;this.y = (typeof y !== 'undefined') ? y : 0;}Point.prototype.clone = function() {return new Point(this.x, this.y);};Point.prototype.length = function(length) {if (typeof length == 'undefined')return Math.sqrt(this.x * this.x + this.y * this.y);this.normalize();this.x *= length;this.y *= length;return this;};Point.prototype.normalize = function() {var length = this.length();this.x /= length;this.y /= length;return this;};return Point;})();/** Particle class*/var Particle = (function() {function Particle() {this.position = new Point();this.velocity = new Point();this.acceleration = new Point();this.age = 0;}Particle.prototype.initialize = function(x, y, dx, dy) {this.position.x = x;this.position.y = y;this.velocity.x = dx;this.velocity.y = dy;this.acceleration.x = dx * settings.particles.effect;this.acceleration.y = dy * settings.particles.effect;this.age = 0;};Particle.prototype.update = function(deltaTime) {this.position.x += this.velocity.x * deltaTime;this.position.y += this.velocity.y * deltaTime;this.velocity.x += this.acceleration.x * deltaTime;this.velocity.y += this.acceleration.y * deltaTime;this.age += deltaTime;};Particle.prototype.draw = function(context, image) {function ease(t) {return (--t) * t * t + 1;}var size = image.width * ease(this.age / settings.particles.duration);context.globalAlpha = 1 - this.age / settings.particles.duration;context.drawImage(image, this.position.x - size / 2, this.position.y - size / 2, size, size);};return Particle;})();/** ParticlePool class*/var ParticlePool = (function() {var particles,firstActive = 0,firstFree = 0,duration = settings.particles.duration;function ParticlePool(length) {// create and populate particle poolparticles = new Array(length);for (var i = 0; i < particles.length; i++)particles[i] = new Particle();}ParticlePool.prototype.add = function(x, y, dx, dy) {particles[firstFree].initialize(x, y, dx, dy);// handle circular queuefirstFree++;if (firstFree == particles.length) firstFree = 0;if (firstActive == firstFree) firstActive++;if (firstActive == particles.length) firstActive = 0;};ParticlePool.prototype.update = function(deltaTime) {var i;// update active particlesif (firstActive < firstFree) {for (i = firstActive; i < firstFree; i++)particles[i].update(deltaTime);}if (firstFree < firstActive) {for (i = firstActive; i < particles.length; i++)particles[i].update(deltaTime);for (i = 0; i < firstFree; i++)particles[i].update(deltaTime);}// remove inactive particleswhile (particles[firstActive].age >= duration && firstActive != firstFree) {firstActive++;if (firstActive == particles.length) firstActive = 0;}};ParticlePool.prototype.draw = function(context, image) {// draw active particlesif (firstActive < firstFree) {for (i = firstActive; i < firstFree; i++)particles[i].draw(context, image);}if (firstFree < firstActive) {for (i = firstActive; i < particles.length; i++)particles[i].draw(context, image);for (i = 0; i < firstFree; i++)particles[i].draw(context, image);}};return ParticlePool;})();/** Putting it all together*/(function(canvas) {var context = canvas.getContext('2d'),particles = new ParticlePool(settings.particles.length),particleRate = settings.particles.length / settings.particles.duration, // particles/sectime;// get point on heart with -PI <= t <= PIfunction pointOnHeart(t) {return new Point(160 * Math.pow(Math.sin(t), 3),130 * Math.cos(t) - 50 * Math.cos(2 * t) - 20 * Math.cos(3 * t) - 10 * Math.cos(4 * t) + 25);}// creating the particle image using a dummy canvasvar image = (function() {var canvas = document.createElement('canvas'),context = canvas.getContext('2d');canvas.width = settings.particles.size;canvas.height = settings.particles.size;// helper function to create the pathfunction to(t) {var point = pointOnHeart(t);point.x = settings.particles.size / 2 + point.x * settings.particles.size / 350;point.y = settings.particles.size / 2 - point.y * settings.particles.size / 350;return point;}// create the pathcontext.beginPath();var t = -Math.PI;var point = to(t);context.moveTo(point.x, point.y);while (t < Math.PI) {t += 0.01; // baby steps!point = to(t);context.lineTo(point.x, point.y);}context.closePath();// create the fillcontext.fillStyle = '#ea80b0';context.fill();// create the imagevar image = new Image();image.src = canvas.toDataURL();return image;})();// render that thing!function render() {// next animation framerequestAnimationFrame(render);// update timevar newTime = new Date().getTime() / 1000,deltaTime = newTime - (time || newTime);time = newTime;// clear canvascontext.clearRect(0, 0, canvas.width, canvas.height);// create new particlesvar amount = particleRate * deltaTime;for (var i = 0; i < amount; i++) {var pos = pointOnHeart(Math.PI - 2 * Math.PI * Math.random());var dir = pos.clone().length(settings.particles.velocity);particles.add(canvas.width / 2 + pos.x, canvas.height / 2 - pos.y, dir.x, -dir.y);}// update and draw particlesparticles.update(deltaTime);particles.draw(context, image);}// handle (re-)sizing of the canvasfunction onResize() {canvas.width = canvas.clientWidth;canvas.height = canvas.clientHeight;}window.onresize = onResize;// delay rendering bootstrapsetTimeout(function() {onResize();render();}, 10);})(document.getElementById('pinkboard'));</script></body></html>
演示
