使用canvas怎么绘制一个烟花效果
这期内容当中小编将会给大家带来有关使用canvas怎么绘制一个烟花效果，文章内容丰富且以专业的角度为大家分析和叙述，阅读完这篇文章希望大家可以有所收获。
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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;
}
@autobind
class FireworkComponent extends React.Component {
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 (
);
}
}
export default FireworkComponent; 上述就是小编为大家分享的使用canvas怎么绘制一个烟花效果了，如果刚好有类似的疑惑，不妨参照上述分析进行理解。如果想知道更多相关知识，欢迎关注创新互联行业资讯频道。
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