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.COMponentPropTypes>
 {
        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。

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