0

遇到以下问题：

来自服务器的条形码图像-> 将其实现到画布上，因此我周围有空白区域，以便使用 quagga.js 更好地定位-> 将结果保存到 base64 -> 使用结果并扫描出条形码数据。

我的代码如下所示：

const srcImage = document.querySelector('#src-image').src
const checkBarcode = document.querySelector('#barcode-check')

let dataURL
function addWhiteSpaceAroundImage(srcImage) {
  const canvas = document.createElement('canvas')
  const ctx = canvas.getContext('2d')

  const image = new Image()
  image.onload = drawImageActualSize
  image.src = srcImage

  function drawImageActualSize() {
    const extraSpace = 100
    canvas.width = this.naturalWidth + extraSpace * 2
    canvas.height = this.naturalHeight + extraSpace * 2

    ctx.fillStyle = '#FFFFFF'
    ctx.fillRect(0, 0, canvas.width, canvas.height)
    ctx.drawImage(this, extraSpace, extraSpace)

    dataURL = canvas.toDataURL('image/png') // <--- i need this dataURL for "decodeBarcode()"
  }
}

function decodeBarcode(image) {
  // TODO: here BASE64 Image from "addWhiteSpaceAroundImage()"
  console.log(image)
  return new Promise((resolve, reject) => {
    Quagga.decodeSingle(
      {
        src: image,
        locate: true,
        decoder: {
          readers: ['code_128_reader'],
        },
      },
      function (result) {
        if (result) {
          resolve(result)
        } else {
          reject(new Error('no detection'))
        }
      }
    )
  })
}

decodeBarcode(dataURL) //<--- is undefined

这是我的HTML：

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Barcode Reader Test</title>
  <style>
    body {
      background-color: rgb(34, 34, 34);
      text-align: center;
    }

    * {
      margin: 20px 0;
    }
  </style>
</head>

<body>
  <img id="src-image"
    src="https://www.cognex.com/library/media/resources/symbologies/code128.jpg?h=250&w=447&la=de-AT&hash=4D254808A9954CB9CAD786F569BE0C78"
    alt=""> <br>
  <!-- <button onclick="addWhiteSpaceAroundImage('barcode_test.png')">Add Whitespace to
    Image</button> <br> -->
  <button id="barcode-check">Check Barcode</button> <br>
  <img id="img-result" src="" alt="">
  <script
    src="https://cdn.jsdelivr.net/npm/@ericblade/quagga2/dist/quagga.min.js"></script>
  <script src="app.js"></script>
</body>

</html>

我知道异步代码肯定有一些问题，但我不知道如何使它工作

4

0 回答 0