canvas实现二维码和图片合成的示例代码

import React, { Component } from 'react'const qrcode = require('jr-qrcode')const loadImg = (src) => {    const paths = Array.isArray(src) ? src : [src];    const promise = [];    paths.forEach((path) => {        promise.push(new Promise((resolve, reject) => {            let img = new Image();            img.crossOrigin = "Anonymous";            img.src = path;            img.onload = () => {                resolve(img);            };            img.onerror = (err) => {                console.log('图片加载失败')            }        }))    });    return Promise.all(promise);}const getImageData = (url, src) => {    const imgsrc = qrcode.getQrBase64(url)    let canvas = document.createElement('canvas')    const width = document.documentElement.clientWidth    const height = document.documentElement.clientHeight    canvas.width = width*2    canvas.height = height*2    let ctx = canvas.getContext("2d")     loadImg([imgsrc, src]).then(([img1, img2]) => {        ctx.drawImage(img2, 0, 0, width*2, height*2)        ctx.drawImage(img1, width-80, height*2-220, 200, 160)        ctx.fillStyle = 'rgba(0,0,0,0.3)';        ctx.fillRect(width-80, height*2-60, 200, 40);        ctx.save()        ctx.font="28px Arial"        ctx.fillStyle = '#fff';        ctx.fillText('长按识别二维码', width-80, height*2-30, 200, 160)        let imageURL = canvas.toDataURL("image/png")        document.getElementById('mix_img').setAttribute('src',imageURL)    })}export default class QRcode extends Component {    render() {        const { url , picSrc} = this.props        getImageData(url,picSrc)        return (            <div>                <img  alt='mix_img' id='mix_img'/>            </div>        )    }}