canvas实现点击下雪动画效果代码-html代码-BFW代码库

canvas实现点击下雪动画效果代码

代码语言：html

所属分类：动画

代码描述：canvas实现点击下雪动画效果代码

下面为部分代码预览，完整代码请点击下载或在bfwstudio webide中打开

<!DOCTYPE html>
<html lang="en" >
<head>
  <meta charset="UTF-8">
<style>
    @import url(https://fonts.bunny.net/css?family=architects-daughter:400);

body {
  margin: 0;
  overflow: hidden;
  background: linear-gradient(to bottom, black,#001f3f, #005f8f);
  height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
  align-items: center;
  
  font-family: 'Architects Daughter', handwriting;
  /*
  background-image: url("https://raw.githubusercontent.com/cbolson/icodethis-challenges/main/assets/images/winter-scene.jpg");
  background-attachment: fixed;
  background-size: cover;
  */
}

canvas {
  display: block;
  position: absolute;
  top: 0;
  left: 0;
}

button {
  position: fixed;
  top: 2rem;
  z-index: 10;
  padding: .75rem 1rem;
  color: #FFF;
  background-color: rgb(225, 29, 72);
  border: 1px solid rgba(255 255 255 / .5);
  border-radius: 5px;
  cursor: pointer;
  font-size: 1.2rem;
  font-family: inherit;
  font-weight: 600;
  box-shadow: 2px 2px 5px 5px rgba(0 0 0 / .5);
  transition: background-color 300ms ease-in-out,opacity 300ms ease-in-out;
}
button:hover{
  background-color: rgb(159, 18, 57);
}

button:disabled{
  opacity: .2;
  cursor: not-allowed;
}
</style>
</head>
<body>

<canvas id="snowCanvas"></canvas>
<button type="button" id="btn-snow">Let it Snow!</button>

  <script >
      
      const canvas = document.getElementById("snowCanvas");
const btnSnow = document.getElementById("btn-snow");
const ctx = canvas.getContext("2d");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;

let snowflakes = [];
let isSnowing = false; 
const MAX_SNOWFLAKE_SIZE = 20;
const NUM_SNOWFLAKES = 200; // Number of snowflakes generated 
const SMALL_SNOWFLAKE_SIZE = 10; // below this size the snowflakes will just be circles to reduce load
const THRESHOLD_SNOWFLAKES = 399; // max num of snowflakes visible at any time

// Adjust canvas size on window resize
window.addEventListener("resize", () => {
  canvas.width = window.innerWidth;
  canvas.height = window.innerHeight;
});

// generate a random snowflake (with creative branches or circle for small ones)
function createSnowflake() {
  const numBranches = Math.floor(Math.random() * 6) + 6;
  const snowflakeRotation = Math.random() * Math.PI * 2;
  const size = Math.min(Math.random() * MAX_SNOWFLAKE_SIZE + 0, MAX_SNOWFLAKE_SIZE);
  const x = Math.random() * canvas.width;
  const y = Math.random() * -canvas.height;
  const branchPattern = size < SMALL_SNOWFLAKE_SIZE ? null : generateRandomBranch(size);

  return {
    x,
    y,
    size,
    numBranches,
    snowflakeRotation,
    branchPattern,
    opacity: Math.random() * 0.8 + 0.2,
    speed: Math.random() * 3 + 1,
    horizontalMovement: (Math.random() - 0.5) * 2,
    rotationSpeed: Math.random() * 0.005 - 0.0025,
  };
}

// draw a snowflake
function drawSymmetricSnowflake(snowflake) {
  ctx.save();
  ctx.translate(snowflake.x, snowflake.y);
  ctx.rotate(snowflake.snowflakeRotation);
  ctx.globalAlpha = snowflake.opacity;

  const scaleFactor = snowflake.size / MAX_SNOWFLAKE_SIZE;
  ctx.scale(scaleFactor, scaleFactor);

  if (snowflake.size < SMALL_SNOWFLAKE_SIZE) {
    drawSimpleCircle(snowflake);
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