爱心

1. 案例简介

最近网剧《点燃我，温暖你》热映，相信广大男同胞的女朋友都在吵着要李洵的❤，没有女朋友的兄弟也要注意，这机会它不就来了吗，博主在刷短视频时也看了部分剪辑，当时震惊我的是那句台词“这次老师布置的可是求三个数里的最大值，你不会是怕自己做不出来所以不敢交作业吧。”这句多少是有些搞笑了，后来也有刷到更新剧集的，就是C语言考试时，考试题目是打印爱心❤，男主写了个动态爱心❤，给女主看懵了，当时就有不祥的预感，果然下午就有人找我要我给她弄一个，C语言咱真做不到，前端的可以试试，这就来上！完整源码在最后，复制就可用(点击目录直接跳转）！
效果如图
在这里插入图片描述

2. 爱心实现

这个案例其实只是简单的一个盒子模型，关键是使用js让这个爱心实现动效，包括爱心边界要由许多跳动的小心心组成，以及在不断缩小实现跳动效果。

2.1 盒子模型

首先自然是一个盒子模型打底，在其中实现爱心的效果

<canvas id="pinkboard"></canvas>
2.2 CSS样式

CSS也比较简单，只是简单的边界修订，包括背景颜色（黑色），大小，宽高等等有的没的。

在这里插入图片描述

html, body {
  height: 100%;
  padding: 0;
  margin: 0;
  background: #000;
}
canvas {
  position: absolute;
  width: 100%;
  height: 100%;
}
2.3 JS实现动效

这个就比较复杂啦，包括动效的方向，动效范围，动效行为类型以及定时等等，利用回调函数实现宽高自适应，因为爱心是要跳动的，大小会改变，这就要求宽高要一起变化，否则会出现特变尴尬的效果，你的爱心可能会比较抽象，，，避免此问题也很简单，直接让宽高产生联系即可，他们一起改变！

范围指定

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;
})();

大致爱心形状
简单画出大致形状，后面去进一步改进边框，让边框也实现动效，这里的关键就是爱心的凹下去的部分，可以把爱心看成是一个圆形，只是发生了一些简单的改变，凹下去一块，突出去一块。
在这里插入图片描述

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;
})();

边界小爱心

这个实现最为麻烦，要设置小爱心的不断更替，以及形状渐变等等，设置定时器，保证每个小爱心的出现时间有规律，这样看起来才会整齐，否则总会有点尴尬的小坚强一直不消散，还有就是要保证小爱心扩散的方向，要结合它所处的位置，如果都是直接朝着一个方向扩散会感觉很奇怪，不符合人类的直观审美，在那个位置的小爱心，就要从那个位置出发去消散，避免诙谐的感受。同时要随着大爱心的大小改变调整自己的出现位置，但是也不能全部出现在内侧，还要有一两个漏网之鱼在外面，有种凌乱美，看起来观感更佳。
在这里插入图片描述

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;
})();

将上述部件组装
这里就还是比较简单的啦，只需要把之前写好的部分按照预想该怎么调用就怎么调用，设置好定时器以及出现位置，因为是心形，还要结合一些数学函数，比如cos等，实现变角处理，让整个心形更加圆滑平稳，还要设置页面的显示方式，渐变出现，以及出现的速度等等。

(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;
  })();

边界处理以及其他设定
这里要设定好小爱心们散落的位置以及出现地址，保证跟随着大爱心一起动，同时圈定大爱心的位置。
在这里插入图片描述

// 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'));

3. 完整源码

相信也有同志可能不是程序员，但被迫找到这里，这个源码只需要复制到一个空的txt文件里，然后把txt的后缀改成html打开就可以啦。

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
 <HEAD>
  <TITLE> New Document </TITLE>
  <META NAME="Generator" CONTENT="EditPlus">
  <META NAME="Author" CONTENT="">
  <META NAME="Keywords" CONTENT="">
  <META NAME="Description" CONTENT="">
  <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 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 Möller
 */
(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 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'));
  </script>
 </BODY>
</HTML>
# 前端 # javascript # html
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