1.了解jsQR

jsQR是一个纯javascript脚本实现的二维码识别库，不仅可以在浏览器端使用，而且支持后端node.js环境。jsQR使用较为简单，有着不错的识别率。

2.效果图

3.二维码

4.下载jsqr包

npm i -d jsqr

5.代码

<script setup>
import { ref } from 'vue'
import jsQR from "jsqr";

const codeVal = ref('');

function decodeQRCode(image) {
  //创建画布
  const canvas = document.createElement('canvas');
  const context = canvas.getContext('2d');
  canvas.width = image.width;
  canvas.height = image.height;
  //把二维码画上去
  context.drawImage(image, 0, 0, canvas.width, canvas.height);
  const imageData = context.getImageData(0, 0, canvas.width, canvas.height);
  //jsQR识别出来
  console.log('识别前的数据',
  imageData.data, imageData.width, imageData.height, 
);
  const decodedResult = jsQR(imageData.data, imageData.width, imageData.height, {
    inversionAttempts: 'dontInvert',
  });
  if (decodedResult) {
    //返回识别结果
    return decodedResult.data
  } else {
    window.alert('未识别到二维码!')
    return ''
  }
}

function upload() {
  let input = document.querySelector('#input')
  const file = input.files[0]
  console.log('文件是什么',file);
  if (file) {
    const reader = new FileReader();
    reader.onload = (e) => {
      const image = new Image();
      image.src = e.target.result;
      image.onload = () => {
        let code = decodeQRCode(image);
        console.log(code)//识别结果 
        codeVal.value = code;
      };
    };
    reader.readAsDataURL(file);
  }
}

</script>

<template>
  <!-- <button @click="$refs.input.click()">识别</button> -->
  <input type="file"  id="input" ref="input" @change="upload">
  <div>识别结果：{{codeVal}}</div>
  <!-- <input type="file" style="display: none" id="input" @input="upload"> -->
</template>