Creating a Blob from a Base64 String in JavaScript

Creating a BLOB from a Base64 string in JavaScript

The atob function will decode a Base64-encoded string into a new string with a character for each byte of the binary data.

const byteCharacters = atob(b64Data);

Each character's code point (charCode) will be the value of the byte. We can create an array of byte values by applying this using the .charCodeAt method for each character in the string.

const byteNumbers = new Array(byteCharacters.length);
for (let i = 0; i < byteCharacters.length; i++) {
    byteNumbers[i] = byteCharacters.charCodeAt(i);
}

You can convert this array of byte values into a real typed byte array by passing it to the Uint8Array constructor.

const byteArray = new Uint8Array(byteNumbers);

This in turn can be converted to a BLOB by wrapping it in an array and passing it to the Blob constructor.

const blob = new Blob([byteArray], {type: contentType});

The code above works. However the performance can be improved a little by processing the byteCharacters in smaller slices, rather than all at once. In my rough testing 512 bytes seems to be a good slice size. This gives us the following function.

const b64toBlob = (b64Data, contentType='', sliceSize=512) => {
  const byteCharacters = atob(b64Data);
  const byteArrays = [];

  for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
    const slice = byteCharacters.slice(offset, offset + sliceSize);

    const byteNumbers = new Array(slice.length);
    for (let i = 0; i < slice.length; i++) {
      byteNumbers[i] = slice.charCodeAt(i);
    }

    const byteArray = new Uint8Array(byteNumbers);
    byteArrays.push(byteArray);
  }

  const blob = new Blob(byteArrays, {type: contentType});
  return blob;
}

const blob = b64toBlob(b64Data, contentType);
const blobUrl = URL.createObjectURL(blob);

window.location = blobUrl;

Full Example:

const b64toBlob = (b64Data, contentType='', sliceSize=512) => {

  const byteCharacters = atob(b64Data);

  const byteArrays = [];

  for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {

    const slice = byteCharacters.slice(offset, offset + sliceSize);

    const byteNumbers = new Array(slice.length);

    for (let i = 0; i < slice.length; i++) {

      byteNumbers[i] = slice.charCodeAt(i);

    }

    const byteArray = new Uint8Array(byteNumbers);

    byteArrays.push(byteArray);

  }

  const blob = new Blob(byteArrays, {type: contentType});

  return blob;

}

const contentType = 'image/png';

const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';

const blob = b64toBlob(b64Data, contentType);

const blobUrl = URL.createObjectURL(blob);

const img = document.createElement('img');

img.src = blobUrl;

document.body.appendChild(img);

Converting base64 to blob in javascript

Try this out. Please note that dataURI is assumed to include base64 prefix. (e.g. "data:image/jpeg;base64,")

function b64toBlob(dataURI) {
    
    var byteString = atob(dataURI.split(',')[1]);
    var ab = new ArrayBuffer(byteString.length);
    var ia = new Uint8Array(ab);
    
    for (var i = 0; i < byteString.length; i++) {
        ia[i] = byteString.charCodeAt(i);
    }
    return new Blob([ab], { type: 'image/jpeg' });
}

Usage:

...

var blob = b64toBlob(imageData);

var formData = new FormData();
formData.append("source", blob);
...

How to reconstruct audio blob from a base64 encoded String?

You're on the right track. I would create a function that converts the URI to pure binary by removing the base64 headers, and then setting that as the audio source. Using your data, this should do the trick:

function convertURIToBinary(dataURI) {

  let BASE64_MARKER = ';base64,';

  let base64Index = dataURI.indexOf(BASE64_MARKER) + BASE64_MARKER.length;

  let base64 = dataURI.substring(base64Index);

  let raw = window.atob(base64);

  let rawLength = raw.length;

  let arr = new Uint8Array(new ArrayBuffer(rawLength));

  for (let i = 0; i < rawLength; i++) {

    arr[i] = raw.charCodeAt(i);

  }

  return arr;

}

let binary = convertURIToBinary(data);

let blob = new Blob([binary], {

  type: 'audio/ogg'

});

let blobUrl = URL.createObjectURL(blob);

$("#source").attr("src", blobUrl);

$("#audio")[0].load(); 

$("#audio")[0].oncanplaythrough = $("#audio")[0].play();

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<audio id="audio" controls>

  <source id="source" src="" type="audio/ogg" />

</audio>

<script>

let data = "data:application/octet-stream;base64,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";

</script>

Convert blob to base64

var reader = new FileReader();
reader.readAsDataURL(blob); 
reader.onloadend = function() {
  var base64data = reader.result;                
  console.log(base64data);
}

Form the docs readAsDataURL encodes to base64

As an awaitable function:

function blobToBase64(blob) {
  return new Promise((resolve, _) => {
    const reader = new FileReader();
    reader.onloadend = () => resolve(reader.result);
    reader.readAsDataURL(blob);
  });
}

Note: The blob's result cannot be directly decoded as Base64 without first removing the Data-URL declaration preceding the Base64-encoded data. To retrieve only the Base64 encoded string, first remove data:/;base64, from the result.

Send a Base64/BLOB image data from PHP to Javascript

 $image = 'yourimage'; 

// Read image path, convert to base64 encoding  
$imageData=base64_encode(file_get_contents($image)); 

// Format the image SRC: data:{mime};base64,{data}; 
$src = 'data: '.mime_content_type($image).';base64,'.$imageData; 

And now the src is urldata and can be ready to be transformed to js.

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