canvas实现烟花的示例代码

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脚本之家。

canvas实现烟花的示例代码