canvas 心

html, body {

height: 100%;

padding: 0;

margin: 0;

background: #000;

}

canvas {

position: absolute;

width: 100%;

height: 100%;

}

/*

* Settings

*/

var settings = {

particles: {

length: 500, // maximum amount of particles

duration: 2, // particle duration in sec

velocity: 100, // particle velocity in pixels/sec

effect: -0.75, // play with this for a nice effect

size: 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

/*

* 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 pool

particles = 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 queue

firstFree++;

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 particles

if (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 particles

while (particles[firstActive].age >= duration && firstActive != firstFree) {

firstActive++;

if (firstActive == particles.length) firstActive = 0;

}

};

ParticlePool.prototype.draw = function(context, image) {

// draw active particles

if (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/sec

time;

// get point on heart with -PI <= t <= PI

function 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 canvas

var 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 path

function 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 path

context.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 fill

context.fillStyle = '#ea80b0';

context.fill();

// create the image

var image = new Image();

image.src = canvas.toDataURL();

return image;

})();

// render that thing!

function render() {

// next animation frame

requestAnimationFrame(render);

// update time

var newTime = new Date().getTime() / 1000,

deltaTime = newTime - (time || newTime);

time = newTime;

// clear canvas

context.clearRect(0, 0, canvas.width, canvas.height);

// create new particles

var 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 particles

particles.update(deltaTime);

particles.draw(context, image);

}

// handle (re-)sizing of the canvas

function onResize() {

canvas.width = canvas.clientWidth;

canvas.height = canvas.clientHeight;

}

window.onresize = onResize;

// delay rendering bootstrap

setTimeout(function() {

onResize();

render();

}, 10);

})(document.getElementById('pinkboard'));

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