小程序解析二维码：jsQR

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
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5.代码

<!-- index.wxml -->
<view class="container">
  <button bindtap="chooseImage">选择图片识别二维码</button>
  <canvas id="qrcodeCanvas" canvas-id="qrcodeCanvas" style="width: {{canvasWidth}}px; height: {{canvasHeight}}px"></canvas>
</view>

<button bind:tap="process">识别</button>
<button style="width: 100vw; margin-top: 20rpx;">识别结果：{{msg}}</button>
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// index.js
import jsQR from "jsqr";

Page({
  data: {
    msg: "",
    canvasWidth: 0,
    canvasHeight: 0,
  },

  chooseImage() {
    wx.vibrateShort();
    wx.chooseMedia({
      count: 1,
      mediaType: ["image"],
      sourceType: ["album", "camera"],
      success: (res) => {
        this.decodeQRCode(res.tempFiles[0].tempFilePath);
      },
      fail: (err) => {
        console.error("选择图片失败", err);
      },
    });
  },

  decodeQRCode(imagePath) {
    wx.getImageInfo({
      src: imagePath,
      success: (imageInfo) => {
        this.setData({
          canvasWidth: imageInfo.width,
          canvasHeight: imageInfo.height,
        });

        const canvasId = "qrcodeCanvas";
        const ctx = wx.createCanvasContext(canvasId);

        ctx.drawImage(imagePath, 0, 0, imageInfo.width, imageInfo.height);
        ctx.draw();
      },
      fail: (err) => {
        console.error("获取图片信息失败", err);
      },
    });
  },

  process() {
    const imageInfo = {
      width: this.data.canvasWidth,
      height: this.data.canvasHeight,
    };
    wx.canvasGetImageData({
      canvasId: "qrcodeCanvas",
      x: 0,
      y: 0,
      width: imageInfo.width,
      height: imageInfo.height,
      success: (res) => {
        console.log(res);
        const imageData = {
          data: res.data,
          width: imageInfo.width,
          height: imageInfo.height,
        };

        // 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",
          }
        );

        console.log("结果", decodedResult);
        if (decodedResult) {
          console.log(decodedResult.data); // 识别结果
          this.setData({
            msg: decodedResult.data,
          });
        } else {
          wx.showToast({
            icon: "none",
            title: "未识别到二维码!",
          });
        }
      },
      fail: (err) => {
        console.error("获取 Canvas 像素数据失败", err);
      },
    });
  },
});

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