图像 Base64 字符串到 Uint8ClampedArray

Question

我有从 Expo ImagePicker component, and I want to convert it to An Uint8ClampedArray of RGBA pixel values in the form [r0, g0, b0, a0, r1, g1, b1, a1, ...], cause it's the only input accepted by jsQR library

返回的 base64 格式的图像数据

我试过了，但没用：

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

React Native 的新答案：

这个包应该可以解决问题。让我知道它是否有效。

https://www.npmjs.com/package/get-image-data

浏览器的旧答案：

首先将 base64 img 放入 canvas 中，如下所述：

Base64 PNG data to HTML5 canvas

然后在您的 canvas (https://developer.mozilla.org/en-US/docs/Web/API/ImageData)

上应用 ImageData

这应该会给你想要的结果。

Answer 2

我找到的解决方案如下：

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];
}

Answer 3

我猜您的 base64 编码 URI 实际上是 PNG，因此您可以执行以下操作：

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

图像 Base64 字符串到 Uint8ClampedArray

Image Base64 string to Uint8ClampedArray

javascript

qr-code

image

react-native