图像 Base64 字符串到 Uint8ClampedArray

Question

我有从Expo ImagePicker 组件返回的 base64 格式的图像数据，我想将其转换为 [r0, g0, b0, a0, r1, g1, b1, a1, ...] 形式的 RGBA 像素值的 Uint8ClampedArray，因为它是jsQR 库接受的唯一输入

我试过这个，但没有用：

const dataURItoBlob = byteString  => {

  // write the bytes of the string to a typed array
  var ia = new Uint8ClampedArray(byteString.length);
  for (var i = 0; i < byteString.length; i++) {
    ia[i] = byteString.charCodeAt(i);
  }

  return ia;
};

任何帮助将不胜感激

Answer 1

我猜你的 base64 编码的 URI 实际上是一个 PNG，所以你可以执行以下操作：

const {PNG} = require('pngjs');
const jsqr = require('jsqr');

const dataUri = 'data:image/png;base64,ABCDEFYOURIMAGEHEREABCDEF';
const png = PNG.sync.read(Buffer.from(dataUri.slice('data:image/png;base64,'.length), 'base64'));
const code = jsqr(Uint8ClampedArray.from(png.data), png.width, png.height);

// code.data now contains the URL string encoded by the QR code

Answer 2

我找到的解决方案如下：

它需要使用typedarray、Buffer、jpeg-js

var Uint8ClampedArray = require('typedarray').Uint8ClampedArray;
const Buffer = require('buffer').Buffer;
global.Buffer = Buffer; // very important
const jpeg = require('jpeg-js');


const jpegData = Buffer.from(base64, 'base64');
var rawImageData = jpeg.decode(jpegData);

var clampedArray = new Uint8ClampedArray(rawImageData.data.length);
// manually fill Uint8ClampedArray, cause Uint8ClampedArray.from function is not available in react-native
var i;
for (i = 0; i < rawImageData.data.length; i++) {
  clampedArray[i] = rawImageData.data[i];
}