html5情人节爱心背景动画特效

使用方法

var canvas = document.querySelector("canvas"),
  ctx = canvas.getContext("2d");

var ww,wh;

function onResize(){
  ww = canvas.width = window.innerWidth;
  wh = canvas.height = window.innerHeight;
}

ctx.strokeStyle = "red";
ctx.shadowBlur = 25;
ctx.shadowColor = "hsla(0, 100%, 60%,0.5)";

var precision = 100;
var hearts = [];
var mouseMoved = false;
function onMove(e){
  mouseMoved = true;
  if(e.type === "touchmove"){
    hearts.push(new Heart(e.touches[0].clientX, e.touches[0].clientY));
    hearts.push(new Heart(e.touches[0].clientX, e.touches[0].clientY));
  }
  else{
    hearts.push(new Heart(e.clientX, e.clientY));
    hearts.push(new Heart(e.clientX, e.clientY));
  }
}

var Heart = function(x,y){
  this.x = x || Math.random()*ww;
  this.y = y || Math.random()*wh;
  this.size = Math.random()*2 + 1;
  this.shadowBlur = Math.random() * 10;
  this.speedX = (Math.random()+0.2-0.6) * 8;
  this.speedY = (Math.random()+0.2-0.6) * 8;
  this.speedSize = Math.random()*0.05 + 0.01;
  this.opacity = 1;
  this.vertices = [];
  for (var i = 0; i < precision; i++) {
    var step = (i / precision - 0.5) * (Math.PI * 2);
    var vector = {
      x : (15 * Math.pow(Math.sin(step), 3)),
      y : -(13 * Math.cos(step) - 5 * Math.cos(2 * step) - 2 * Math.cos(3 * step) - Math.cos(4 * step)) 
    }
    this.vertices.push(vector);
  }
}

Heart.prototype.draw = function(){
  this.size -= this.speedSize;
  this.x += this.speedX;
  this.y += this.speedY;
  ctx.save();
  ctx.translate(-1000,this.y);
  ctx.scale(this.size, this.size);
  ctx.beginPath();
  for (var i = 0; i < precision; i++) {
    var vector = this.vertices[i];
    ctx.lineTo(vector.x, vector.y);
  }
  ctx.globalAlpha = this.size;
  ctx.shadowBlur = Math.round((3 - this.size) * 10);
  ctx.shadowColor = "hsla(0, 100%, 60%,0.5)";
  ctx.shadowOffsetX = this.x + 1000;
  ctx.globalCompositeOperation = "screen"
  ctx.closePath();
  ctx.fill()
  ctx.restore();
};


function render(a){
  requestAnimationFrame(render);
  
  hearts.push(new Heart())
  ctx.clearRect(0,0,ww,wh);
  for (var i = 0; i < hearts.length; i++) {
    hearts[i].draw();
    if(hearts[i].size <= 0){
      hearts.splice(i,1);
      i--;
    }
  }
}


onResize();
window.addEventListener("mousemove", onMove);
window.addEventListener("touchmove", onMove);
window.addEventListener("resize", onResize);
requestAnimationFrame(render);