canvas实现烟花的示例代码

技术  /  管理员 发布于 7年前   159

前言：马上过年了，我打算在后台里面偷偷地埋个新春祝福+放烟花的彩蛋。项目是基于react+typescript的，因此最后封装成了一个组件，设置好开启时间就可以显示了。

目录结构

目录结构大致如下

我们将烟花分为两个阶段，一个是未炸开持续上升时期，另一个是炸开后分散的时期。
其中Vector表示一个坐标，Particle表示一个烟花的亮点，Firewor表示烟花未炸开时持续上升的亮点。index.tsx就是组件了，绘制了canvas，并执行了动画。

Vector

这个坐标就很简单，后面涉及到位置的变更都可以使用它的add方法进行偏移操作

export default class Vector {    constructor(public x: number, public y: number) {}    add(vec2: {x: number; y: number}) {        this.x = this.x + vec2.x;        this.y = this.y + vec2.y;    }}

Particle

初始创建的时候给个坐标，后续每次更新的时候控制y坐标下落，gravity变量就是下落的值。timeSpan用于控制烟花展示的时长

import Vector from './Vector';export default class Particle {    pos: Vector = null;    vel: {x: number; y: number} = null;    dead: boolean = false;    start: number = 0;    ctx: CanvasRenderingContext2D = null;    constructor(pos: {x: number; y: number}, vel: {x: number; y: number}, ctx: CanvasRenderingContext2D) {        this.pos = new Vector(pos.x, pos.y);        this.vel = vel;        this.dead = false;        this.start = 0;        this.ctx = ctx;    }    update(time: number, gravity: number) {        let timeSpan = time - this.start;        if (timeSpan > 500) {this.dead = true;        }        if (!this.dead) {this.pos.add(this.vel);this.vel.y = this.vel.y + gravity;        }    }    draw() {        if (!this.dead) {this.drawDot(this.pos.x, this.pos.y, Math.random() > 0.5 ? 1 : 2);        }    }    drawDot(x: number, y: number, size: number) {        this.ctx.beginPath();        this.ctx.arc(x, y, size, 0, Math.PI * 2);        this.ctx.fill();        this.ctx.closePath();    }}

Firework

生成随机的hsl颜色，hsl(' + rndNum(360) + ', 100%, 60%);Firework每次上升的距离是一个递减的过程，我们初始设置一个上升的距离，之后每次绘制的时候，这个距离减gravity，当距离小于零的时候，说明该出现烟花绽放的动画了。

import Vector from './Vector';import Particle from './Particle';let rnd = Math.random;function rndNum(num: number) {    return rnd() * num + 1;}export default class Firework {    pos: Vector = null;    vel: Vector = null;    color: string = null;    size: number = 0;    dead: boolean = false;    start: number = 0;    ctx: CanvasRenderingContext2D = null;    gravity: number = null;    exParticles: Particle[] = [];    exPLen: number = 100;    rootShow: boolean = true;    constructor(x: number, y: number, gravity: number, ctx: CanvasRenderingContext2D) {        this.pos = new Vector(x, y);        this.vel = new Vector(0, -rndNum(10) - 3);        this.color = 'hsl(' + rndNum(360) + ', 100%, 60%)';        this.size = 4;        this.dead = false;        this.start = 0;        this.ctx = ctx;        this.gravity = gravity;    }    update(time: number, gravity: number) {        if (this.dead) {return;        }        this.rootShow = this.vel.y < 0;        if (this.rootShow) {this.pos.add(this.vel);this.vel.y = this.vel.y + gravity;        } else {if (this.exParticles.length === 0) {    for (let i = 0; i < this.exPLen; i++) {        let randomR = rndNum(5);        let randomX = -rndNum(Math.abs(randomR) * 2) + Math.abs(randomR);        let randomY =Math.sqrt(Math.abs(Math.pow(randomR, 2) - Math.pow(randomX, 2))) *(Math.random() > 0.5 ? 1 : -1);        this.exParticles.push(new Particle(this.pos, new Vector(randomX, randomY), this.ctx));        this.exParticles[this.exParticles.length - 1].start = time;    }}let numOfDead = 0;for (let i = 0; i < this.exPLen; i++) {    let p = this.exParticles[i];    p.update(time, this.gravity);    if (p.dead) {        numOfDead++;    }}if (numOfDead === this.exPLen) {    this.dead = true;}        }    }    draw() {        if (this.dead) {return;        }        this.ctx.fillStyle = this.color;        if (this.rootShow) {this.drawDot(this.pos.x, this.pos.y, this.size);        } else {for (let i = 0; i < this.exPLen; i++) {    let p = this.exParticles[i];    p.draw();}        }    }    drawDot(x: number, y: number, size: number) {        this.ctx.beginPath();        this.ctx.arc(x, y, size, 0, Math.PI * 2);        this.ctx.fill();        this.ctx.closePath();    }}

FireworkComponent

组件本身就很简单了，生成和绘制Firework。我们在这里面可以额外加一些文字

import React from 'react';import Firework from './Firework';import {autobind} from 'core-decorators';let rnd = Math.random;function rndNum(num: number) {    return rnd() * num + 1;}interface PropTypes {    onClick?: () => void;}@autobindclass FireworkComponent extends React.Component<PropTypes> {    canvas: HTMLCanvasElement = null;    ctx: CanvasRenderingContext2D = null;    snapTime: number = 0;    fireworks: Firework[] = [];    gravity: number = 0.1;    componentDidMount() {        this.canvas = document.querySelector('#fireworks');        this.canvas.width = window.innerWidth;        this.canvas.height = window.innerHeight;        this.ctx = this.canvas.getContext('2d');        this.init();        this.draw();    }    init() {        let numOfFireworks = 20;        for (let i = 0; i < numOfFireworks; i++) {this.fireworks.push(new Firework(rndNum(this.canvas.width), this.canvas.height, this.gravity, this.ctx));        }    }    update(time: number) {        for (let i = 0, len = this.fireworks.length; i < len; i++) {let p = this.fireworks[i];p.update(time, this.gravity);        }    }    draw(time?: number) {        this.update(time);        this.ctx.fillStyle = 'rgba(0,0,0,0.3)';        this.ctx.fillStyle = 'rgba(0,0,0,0)';        this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);        this.ctx.font = 'bold 30px cursive';        this.ctx.fillStyle = '#e91818';        let text = 'XX项目组给您拜个早年！';        let textWidth = this.ctx.measureText(text);        this.ctx.fillText(text, this.canvas.width / 2 - textWidth.width / 2, 200);        text = '在新年来临之际，祝您：';        textWidth = this.ctx.measureText(text);        this.ctx.fillText(text, this.canvas.width / 2 - textWidth.width / 2, 260);        text = '工作顺利，新春快乐!';        this.ctx.font = 'bold 48px STCaiyun';        this.ctx.fillStyle = 'orangered';        textWidth = this.ctx.measureText(text);        this.ctx.fillText(text, this.canvas.width / 2 - textWidth.width / 2, 340);        this.ctx.fillStyle = 'gray';        this.ctx.font = '18px Arial';        text = '点击任意处关闭';        textWidth = this.ctx.measureText(text);        this.ctx.fillText(text, this.canvas.width - 20 - textWidth.width, 60);        this.snapTime = time;        this.ctx.fillStyle = 'blue';        for (let i = 0, len = this.fireworks.length; i < len; i++) {let p = this.fireworks[i];if (p.dead) {    p = this.fireworks[i] = new Firework(        rndNum(this.canvas.width),        this.canvas.height,        this.gravity,        this.ctx    );    p.start = time;}p.draw();        }        window.requestAnimationFrame(this.draw);    }    render() {        return (<canvas    id="fireworks"    onClick={this.props.onClick}    style={{position: 'fixed', zIndex: 99, background: 'rgba(0,0,0, 0.8)'}}    width="400"    height="400"></canvas>        );    }}export default FireworkComponent;

大致效果

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。