如何使用canvas绘制李峋同款爱心?

w3cschool小编 2022-11-11 15:53:11 浏览数 (3384)
反馈

昨天晚上,小编的朋友在聊天的时候谈到了这个:


小编一时间觉得好像与世界脱轨,百度找了一下,终于知道了,原来是最近很火的电视剧《点燃我,温暖你》的一幕:

 朱韵看见了李珣写的代码竟然如此简单,不得不佩服李珣的能力。回去后,朱韵还是想解开李珣的代码,但是尝试了很久竟然打开了,结果一看竟然是一颗跳动的爱心,没想到李珣做的代码竟然比任何人都做的更好。朱韵也不得不佩服李珣的实力,其实当时朱韵U盘上的病毒也是李珣解开的,高见鸿也是听吴孟兴说的,高见鸿倒是觉得可以将兴趣小组解散了,朱韵也只好答应了。
                                                                                                                                         ——本处内容来自搜视网的剧情介绍

好嘛,真会玩,让我们来看看大概长啥样:


我们安排一下!

技术实现

我们使用HTML的canvas进行图案的绘制,这样绘制出来的图案手机电脑都能看!

一般来说html,css,JavaScript要分开写,因为我们的代码量比较少,我们直接写在一起,以下就是具体的代码实现:

爱心.html

<html lang="">
  <head>
    <meta charset="utf-8" />
    <title>爱心代码</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" width="1873" height="218"></canvas>
    <script>
      var settings = {
        particles: {
          length: 500,
          duration: 2,
          velocity: 100,
          effect: -0.75,
          size: 32,
        },
      };
      (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);
          };
        }
      })();

      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;
      })();
      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;
      })();
      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);
          }
          // 移除非活性粒子
          while (
            particles[firstActive].age >= duration &&
            firstActive != firstFree
          ) {
            firstActive++;
            if (firstActive == particles.length) firstActive = 0;
          }
        };
        ParticlePool.prototype.draw = function (context, image) {
          // 绘制活性粒子
          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;
      })();
      (function (canvas) {
        var context = canvas.getContext("2d"),
          particles = new ParticlePool(settings.particles.length),
          particleRate =
            settings.particles.length / settings.particles.duration, // particles/sec
          time;
        // 用-PI<=t<=PI获得心脏点
        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
          );
        }
        // 使用虚拟画布创建粒子图像
        var image = (function () {
          var canvas = document.createElement("canvas"),
            context = canvas.getContext("2d");
          canvas.width = settings.particles.size;
          canvas.height = settings.particles.size;
          // helper函数创建路径
          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;
          }
          // 创建路径
          context.beginPath();
          var t = -Math.PI;
          var point = to(t);
          context.moveTo(point.x, point.y);
          while (t < Math.PI) {
            t += 0.01;
            point = to(t);
            context.lineTo(point.x, point.y);
          }
          context.closePath();
          // 创建填充
          context.fillStyle = "#ea80b0";
          context.fill();
          // 创建图像
          var image = new Image();
          image.src = canvas.toDataURL();
          return image;
        })();
        // 渲染
        function render() {
          // 下一动画帧
          requestAnimationFrame(render);
          var newTime = new Date().getTime() / 1000,
            deltaTime = newTime - (time || newTime);
          time = newTime;
          // 清除画布
          context.clearRect(0, 0, canvas.width, canvas.height);
          // 创建新粒子
          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
            );
          }
          // 更新和绘制粒子
          particles.update(deltaTime);
          particles.draw(context, image);
        }
        // 处理(重新)画布的大小
        function onResize() {
          canvas.width = canvas.clientWidth;
          canvas.height = canvas.clientHeight;
        }
        window.onresize = onResize;
        //延迟渲染
        setTimeout(function () {
          onResize();
          render();
        }, 10);
      })(document.getElementById("pinkboard"));
    </script>
  </body>
</html>

运行结果如下:


canvas是前端最强大的绘制工具,我们可以拿他来作图,也可以拿来做游戏,更多canvas的相关学习内容可以前往Canvas入门到项目实战学习!


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