canvas星空粒子特效

原创于 2024-04-18 18:00:00 发布 · 389 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#javascript #开发语言 #ecmascript #canvas

本文介绍了如何使用Vue.js结合HTML5canvasAPI创建一个具有动态效果的星空粒子动画，包括离屏渲染、颜色渐变和星星运动逻辑。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

canvas星空粒子特效

在这里插入图片描述

<template>
  <div>
    <canvas id="star"></canvas>
  </div>
</template>

<script setup lang="ts">
import { onMounted } from 'vue'


function maxOrbit(x, y) {
  let max = Math.max(x, y),
    diameter = Math.round(Math.sqrt(max * max + max * max));
  return diameter / 2;
}

function random(min, max?: number) {
  if(arguments.length < 2) {
    max = min;
    min = 0;
  }

  if(min > max) {
    let hold = max;
    max = min;
    min = hold;
  }

  return Math.floor(Math.random() * (max - min + 1)) + min;
}

const init = () => {
  let canvas = document.querySelector('#star') as HTMLCanvasElement
    , ctx = canvas.getContext('2d') as CanvasRenderingContext2D,
    w = canvas.width = window.innerWidth,
    h = canvas.height = window.innerHeight,
    // 色相值
    hue = 217,
    // 星星实例的集合
    stars = [],
    // 当前渲染星星的数量
    count = 0,
    // 最大可渲染数量
    maxStars = 1000;

  // 离屏渲染，在屏幕外渲染一个canvas，把当前渲染好的canvas，再渲染到页面可视的canvas上
  let canvas2 = document.createElement('canvas'),
    ctx2 = canvas2.getContext('2d');
  canvas2.width = 100;
  canvas2.height = 100;
  let half = canvas2.width / 2,
    gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half);
  gradient2.addColorStop(0.025, '#fff');
  gradient2.addColorStop(0.1, 'hsl(' + hue + ', 61%, 33%)');
  gradient2.addColorStop(0.25, 'hsl(' + hue + ', 64%, 6%)');
  gradient2.addColorStop(1, 'transparent');

  ctx2.fillStyle = gradient2;
  ctx2.beginPath();
  ctx2.arc(half, half, half, 0, Math.PI * 2);
  ctx2.fill();

  const Star = function() {
    this.orbitRadius = random(maxOrbit(w, h)); // 随机轨道
    this.radius = random(60, this.orbitRadius) / 12; // 星星半径
    this.orbitX = w / 2; //中心x
    this.orbitY = h / 2; // 中心y
    this.timePassed = random(0, maxStars); // 用于控制星星的轨道的相对位置
    this.speed = random(this.orbitRadius) / 50000; // 随机速度
    this.alpha = random(2, 10) / 10; // 随机透明度
    count++;
    stars[count] = this;
  }
  for(let i = 0; i < maxStars; i++) {
    new Star();
  }

  Star.prototype.draw = function() {
    let x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX,
      y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY,
      twinkle = random(10);

    if(twinkle === 1 && this.alpha > 0) {
      this.alpha -= 0.05;
    } else if(twinkle === 2 && this.alpha < 1) {
      this.alpha += 0.05;
    }

    ctx.globalAlpha = this.alpha;
    ctx.drawImage(canvas2, x - this.radius / 2, y - this.radius / 2, this.radius, this.radius);
    this.timePassed += this.speed;
  }

  function animation() {
    ctx.globalCompositeOperation = 'source-over';
    ctx.globalAlpha = 0.8;
    ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 1)';
    ctx.fillRect(0, 0, w, h)

    ctx.globalCompositeOperation = 'lighter';
    for(let i = 1, l = stars.length; i < l; i++) {
      stars[i].draw();
    };

    window.requestAnimationFrame(animation);
  }

  animation()
}
onMounted(() => {
  init()
})
</script>

<style scoped></style>