Related
I have Base64-encoded binary data in a string:
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
I would like to create a blob: URL containing this data and display it to the user:
const blob = new Blob(????, {type: contentType});
const blobUrl = URL.createObjectURL(blob);
window.location = blobUrl;
I haven't been been able to figure out how to create the BLOB.
In some cases I am able to avoid this by using a data: URL instead:
const dataUrl = `data:${contentType};base64,${b64Data}`;
window.location = dataUrl;
However, in most cases the data: URLs are prohibitively large.
How can I decode a Base64 string to a BLOB object 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);
Here is a more minimal method without any dependencies or libraries.
It requires the new fetch API. (Can I use it?)
var url = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=="
fetch(url)
.then(res => res.blob())
.then(console.log)
With this method you can also easily get a ReadableStream, ArrayBuffer, text, and JSON.
(fyi this also works with node-fetch in Node)
As a function:
const b64toBlob = (base64, type = 'application/octet-stream') =>
fetch(`data:${type};base64,${base64}`).then(res => res.blob())
But I would encourage you to don't use base64 in the first place. There are better ways to send and receive binary data. JSON isn't always the best option. it takes up more bandwidth and waste processing time (de)encodeing stuff. Us eg canvas.toBlob instead of canvas.toDataURL and use FormData to send binary files. you can also return back a multipart payload and decode it using await response.formData() that is coming from a server response. FormData can go both ways.
I did a simple performance test towards Jeremy's ES6 sync version.
The sync version will block UI for a while.
keeping the devtool open can slow the fetch performance
document.body.innerHTML += '<input autofocus placeholder="try writing">'
// get some dummy gradient image
var img=function(){var a=document.createElement("canvas"),b=a.getContext("2d"),c=b.createLinearGradient(0,0,1500,1500);a.width=a.height=3000;c.addColorStop(0,"red");c.addColorStop(1,"blue");b.fillStyle=c;b.fillRect(0,0,a.width,a.height);return a.toDataURL()}();
async function perf() {
const blob = await fetch(img).then(res => res.blob())
// turn it to a dataURI
const url = img
const b64Data = url.split(',')[1]
// Jeremy Banks solution
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;
}
// bench blocking method
let i = 500
console.time('blocking b64')
while (i--) {
await b64toBlob(b64Data)
}
console.timeEnd('blocking b64')
// bench non blocking
i = 500
// so that the function is not reconstructed each time
const toBlob = res => res.blob()
console.time('fetch')
while (i--) {
await fetch(url).then(toBlob)
}
console.timeEnd('fetch')
console.log('done')
}
perf()
Optimized (but less readable) implementation:
function base64toBlob(base64Data, contentType) {
contentType = contentType || '';
var sliceSize = 1024;
var byteCharacters = atob(base64Data);
var bytesLength = byteCharacters.length;
var slicesCount = Math.ceil(bytesLength / sliceSize);
var byteArrays = new Array(slicesCount);
for (var sliceIndex = 0; sliceIndex < slicesCount; ++sliceIndex) {
var begin = sliceIndex * sliceSize;
var end = Math.min(begin + sliceSize, bytesLength);
var bytes = new Array(end - begin);
for (var offset = begin, i = 0; offset < end; ++i, ++offset) {
bytes[i] = byteCharacters[offset].charCodeAt(0);
}
byteArrays[sliceIndex] = new Uint8Array(bytes);
}
return new Blob(byteArrays, { type: contentType });
}
Following is my TypeScript code which can be converted easily into JavaScript and you can use
/**
* Convert BASE64 to BLOB
* #param base64Image Pass Base64 image data to convert into the BLOB
*/
private convertBase64ToBlob(base64Image: string) {
// Split into two parts
const parts = base64Image.split(';base64,');
// Hold the content type
const imageType = parts[0].split(':')[1];
// Decode Base64 string
const decodedData = window.atob(parts[1]);
// Create UNIT8ARRAY of size same as row data length
const uInt8Array = new Uint8Array(decodedData.length);
// Insert all character code into uInt8Array
for (let i = 0; i < decodedData.length; ++i) {
uInt8Array[i] = decodedData.charCodeAt(i);
}
// Return BLOB image after conversion
return new Blob([uInt8Array], { type: imageType });
}
See this example: https://jsfiddle.net/pqhdce2L/
function b64toBlob(b64Data, contentType, sliceSize) {
contentType = contentType || '';
sliceSize = sliceSize || 512;
var byteCharacters = atob(b64Data);
var byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
var slice = byteCharacters.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
var blob = new Blob(byteArrays, {type: contentType});
return blob;
}
var contentType = 'image/png';
var b64Data = Your Base64 encode;
var blob = b64toBlob(b64Data, contentType);
var blobUrl = URL.createObjectURL(blob);
var img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
For all browser support, especially on Android, perhaps you can add this:
try{
blob = new Blob(byteArrays, {type : contentType});
}
catch(e){
// TypeError old Google Chrome and Firefox
window.BlobBuilder = window.BlobBuilder ||
window.WebKitBlobBuilder ||
window.MozBlobBuilder ||
window.MSBlobBuilder;
if(e.name == 'TypeError' && window.BlobBuilder){
var bb = new BlobBuilder();
bb.append(byteArrays);
blob = bb.getBlob(contentType);
}
else if(e.name == "InvalidStateError"){
// InvalidStateError (tested on FF13 WinXP)
blob = new Blob(byteArrays, {type : contentType});
}
else{
// We're screwed, blob constructor unsupported entirely
}
}
For all copy-paste lovers out there like me, here is a cooked download function which works on Chrome, Firefox and Edge:
window.saveFile = function (bytesBase64, mimeType, fileName) {
var fileUrl = "data:" + mimeType + ";base64," + bytesBase64;
fetch(fileUrl)
.then(response => response.blob())
.then(blob => {
var link = window.document.createElement("a");
link.href = window.URL.createObjectURL(blob, { type: mimeType });
link.download = fileName;
document.body.appendChild(link);
link.click();
document.body.removeChild(link);
});
}
I'm posting a more declarative way of sync Base64 converting. While async fetch().blob() is very neat and I like this solution a lot, it doesn't work on Internet Explorer 11 (and probably Edge - I haven't tested this one), even with the polyfill - take a look at my comment to Endless' post for more details.
const blobPdfFromBase64String = base64String => {
const byteArray = Uint8Array.from(
atob(base64String)
.split('')
.map(char => char.charCodeAt(0))
);
return new Blob([byteArray], { type: 'application/pdf' });
};
Bonus
If you want to print it you could do something like:
const isIE11 = !!(window.navigator && window.navigator.msSaveOrOpenBlob); // Or however you want to check it
const printPDF = blob => {
try {
isIE11
? window.navigator.msSaveOrOpenBlob(blob, 'documents.pdf')
: printJS(URL.createObjectURL(blob)); // http://printjs.crabbly.com/
} catch (e) {
throw PDFError;
}
};
Bonus x 2 - Opening a BLOB file in new tab for Internet Explorer 11
If you're able to do some preprocessing of the Base64 string on the server you could expose it under some URL and use the link in printJS :)
For image data, I find it simpler to use canvas.toBlob (asynchronous)
function b64toBlob(b64, onsuccess, onerror) {
var img = new Image();
img.onerror = onerror;
img.onload = function onload() {
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var ctx = canvas.getContext('2d');
ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
canvas.toBlob(onsuccess);
};
img.src = b64;
}
var base64Data = 'data:image/jpg;base64,/9j/4AAQSkZJRgABAQA...';
b64toBlob(base64Data,
function(blob) {
var url = window.URL.createObjectURL(blob);
// do something with url
}, function(error) {
// handle error
});
If you can stand adding one dependency to your project there's the great blob-util npm package that provides a handy base64StringToBlob function. Once added to your package.json you can use it like this:
import { base64StringToBlob } from 'blob-util';
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
const blob = base64StringToBlob(b64Data, contentType);
// Do whatever you need with your blob...
I noticed that Internet Explorer 11 gets incredibly slow when slicing the data like Jeremy suggested. This is true for Chrome, but Internet Explorer seems to have a problem when passing the sliced data to the Blob-Constructor. On my machine, passing 5 MB of data makes Internet Explorer crash and memory consumption is going through the roof. Chrome creates the blob in no time.
Run this code for a comparison:
var byteArrays = [],
megaBytes = 2,
byteArray = new Uint8Array(megaBytes*1024*1024),
block,
blobSlowOnIE, blobFastOnIE,
i;
for (i = 0; i < (megaBytes*1024); i++) {
block = new Uint8Array(1024);
byteArrays.push(block);
}
//debugger;
console.profile("No Slices");
blobSlowOnIE = new Blob(byteArrays, { type: 'text/plain'});
console.profileEnd();
console.profile("Slices");
blobFastOnIE = new Blob([byteArray], { type: 'text/plain'});
console.profileEnd();
So I decided to include both methods described by Jeremy in one function. Credits go to him for this.
function base64toBlob(base64Data, contentType, sliceSize) {
var byteCharacters,
byteArray,
byteNumbers,
blobData,
blob;
contentType = contentType || '';
byteCharacters = atob(base64Data);
// Get BLOB data sliced or not
blobData = sliceSize ? getBlobDataSliced() : getBlobDataAtOnce();
blob = new Blob(blobData, { type: contentType });
return blob;
/*
* Get BLOB data in one slice.
* => Fast in Internet Explorer on new Blob(...)
*/
function getBlobDataAtOnce() {
byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
byteArray = new Uint8Array(byteNumbers);
return [byteArray];
}
/*
* Get BLOB data in multiple slices.
* => Slow in Internet Explorer on new Blob(...)
*/
function getBlobDataSliced() {
var slice,
byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
slice = byteCharacters.slice(offset, offset + sliceSize);
byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
byteArray = new Uint8Array(byteNumbers);
// Add slice
byteArrays.push(byteArray);
}
return byteArrays;
}
}
The method with fetch is the best solution, but if anyone needs to use a method without fetch then here it is, as the ones mentioned previously didn't work for me:
function makeblob(dataURL) {
const BASE64_MARKER = ';base64,';
const parts = dataURL.split(BASE64_MARKER);
const contentType = parts[0].split(':')[1];
const raw = window.atob(parts[1]);
const rawLength = raw.length;
const uInt8Array = new Uint8Array(rawLength);
for (let i = 0; i < rawLength; ++i) {
uInt8Array[i] = raw.charCodeAt(i);
}
return new Blob([uInt8Array], { type: contentType });
}
In browser just
Uint8Array.from(atob(YOUR_BASE64_DATA), (c) => c.charCodeAt(0))
compare with fetch
!(async () => {
const start = performance.now();
let i = 0;
while (i++ < 1e3) {
const dataUrl =
"data:application/octet-stream;base64,H4sIAAAAAAAAA0vOzyvOz0nVy8lP10jISM3JyVdIr8osUFCpdkksSdXLyy/X0KxN0ORKHlU3qm5U3ai6UXWj6kauOgBVt1KRLwcAAA==";
body = await (await fetch(dataUrl)).blob();
}
console.log(performance.now() - start); // 508.19999999925494ms
})();
!(async () => {
const start = performance.now();
let i = 0;
while (i++ < 1e3) {
const base64Data =
"H4sIAAAAAAAAA0vOzyvOz0nVy8lP10jISM3JyVdIr8osUFCpdkksSdXLyy/X0KxN0ORKHlU3qm5U3ai6UXWj6kauOgBVt1KRLwcAAA==";
body = Uint8Array.from(atob(base64Data), (c) => c.charCodeAt(0));
}
console.log(performance.now() - start); // 7.899999998509884ms
})();
Depends on your data size, choose performance one.
Two different variations
function base64ToBlob(base64, contentType='image/png', chunkLength=512) {
const byteCharsArray = Array.from(atob(base64.substr(base64.indexOf(',') + 1)));
const chunksIterator = new Array(Math.ceil(byteCharsArray.length / chunkLength));
const bytesArrays = [];
for (let c = 0; c < chunksIterator.length; c++) {
bytesArrays.push(new Uint8Array(byteCharsArray.slice(c * chunkLength, chunkLength * (c + 1)).map(s => s.charCodeAt(0))));
}
const blob = new Blob(bytesArrays, {type: contentType});
return blob;
}
/* Not sure how it performs with big images */
async function base64ToBlobLight(base64) { return await fetch(base64).then(res => res.blob()); }
/* Test */
const base64Data = 'data:image/png;base64,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';
const blob = base64ToBlob(base64Data);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
/**********************/
/* Test */
(async () => {
const blob = await base64ToBlobLight(base64Data);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
})();
This would prove to be much short solution.
const byteArray = new Buffer(base64String.replace(/^[\w\d;:\/]+base64\,/g, ''), 'base64');
base64String is the string containing the base 64 string.
byteArray is the array you need.
The regex replacement is optional and is just there to deal with prefix as in the case of dataurl string.
I have Base64-encoded binary data in a string:
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
I would like to create a blob: URL containing this data and display it to the user:
const blob = new Blob(????, {type: contentType});
const blobUrl = URL.createObjectURL(blob);
window.location = blobUrl;
I haven't been been able to figure out how to create the BLOB.
In some cases I am able to avoid this by using a data: URL instead:
const dataUrl = `data:${contentType};base64,${b64Data}`;
window.location = dataUrl;
However, in most cases the data: URLs are prohibitively large.
How can I decode a Base64 string to a BLOB object 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);
Here is a more minimal method without any dependencies or libraries.
It requires the new fetch API. (Can I use it?)
var url = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=="
fetch(url)
.then(res => res.blob())
.then(console.log)
With this method you can also easily get a ReadableStream, ArrayBuffer, text, and JSON.
(fyi this also works with node-fetch in Node)
As a function:
const b64toBlob = (base64, type = 'application/octet-stream') =>
fetch(`data:${type};base64,${base64}`).then(res => res.blob())
But I would encourage you to don't use base64 in the first place. There are better ways to send and receive binary data. JSON isn't always the best option. it takes up more bandwidth and waste processing time (de)encodeing stuff. Us eg canvas.toBlob instead of canvas.toDataURL and use FormData to send binary files. you can also return back a multipart payload and decode it using await response.formData() that is coming from a server response. FormData can go both ways.
I did a simple performance test towards Jeremy's ES6 sync version.
The sync version will block UI for a while.
keeping the devtool open can slow the fetch performance
document.body.innerHTML += '<input autofocus placeholder="try writing">'
// get some dummy gradient image
var img=function(){var a=document.createElement("canvas"),b=a.getContext("2d"),c=b.createLinearGradient(0,0,1500,1500);a.width=a.height=3000;c.addColorStop(0,"red");c.addColorStop(1,"blue");b.fillStyle=c;b.fillRect(0,0,a.width,a.height);return a.toDataURL()}();
async function perf() {
const blob = await fetch(img).then(res => res.blob())
// turn it to a dataURI
const url = img
const b64Data = url.split(',')[1]
// Jeremy Banks solution
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;
}
// bench blocking method
let i = 500
console.time('blocking b64')
while (i--) {
await b64toBlob(b64Data)
}
console.timeEnd('blocking b64')
// bench non blocking
i = 500
// so that the function is not reconstructed each time
const toBlob = res => res.blob()
console.time('fetch')
while (i--) {
await fetch(url).then(toBlob)
}
console.timeEnd('fetch')
console.log('done')
}
perf()
Optimized (but less readable) implementation:
function base64toBlob(base64Data, contentType) {
contentType = contentType || '';
var sliceSize = 1024;
var byteCharacters = atob(base64Data);
var bytesLength = byteCharacters.length;
var slicesCount = Math.ceil(bytesLength / sliceSize);
var byteArrays = new Array(slicesCount);
for (var sliceIndex = 0; sliceIndex < slicesCount; ++sliceIndex) {
var begin = sliceIndex * sliceSize;
var end = Math.min(begin + sliceSize, bytesLength);
var bytes = new Array(end - begin);
for (var offset = begin, i = 0; offset < end; ++i, ++offset) {
bytes[i] = byteCharacters[offset].charCodeAt(0);
}
byteArrays[sliceIndex] = new Uint8Array(bytes);
}
return new Blob(byteArrays, { type: contentType });
}
Following is my TypeScript code which can be converted easily into JavaScript and you can use
/**
* Convert BASE64 to BLOB
* #param base64Image Pass Base64 image data to convert into the BLOB
*/
private convertBase64ToBlob(base64Image: string) {
// Split into two parts
const parts = base64Image.split(';base64,');
// Hold the content type
const imageType = parts[0].split(':')[1];
// Decode Base64 string
const decodedData = window.atob(parts[1]);
// Create UNIT8ARRAY of size same as row data length
const uInt8Array = new Uint8Array(decodedData.length);
// Insert all character code into uInt8Array
for (let i = 0; i < decodedData.length; ++i) {
uInt8Array[i] = decodedData.charCodeAt(i);
}
// Return BLOB image after conversion
return new Blob([uInt8Array], { type: imageType });
}
See this example: https://jsfiddle.net/pqhdce2L/
function b64toBlob(b64Data, contentType, sliceSize) {
contentType = contentType || '';
sliceSize = sliceSize || 512;
var byteCharacters = atob(b64Data);
var byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
var slice = byteCharacters.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
var blob = new Blob(byteArrays, {type: contentType});
return blob;
}
var contentType = 'image/png';
var b64Data = Your Base64 encode;
var blob = b64toBlob(b64Data, contentType);
var blobUrl = URL.createObjectURL(blob);
var img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
For all browser support, especially on Android, perhaps you can add this:
try{
blob = new Blob(byteArrays, {type : contentType});
}
catch(e){
// TypeError old Google Chrome and Firefox
window.BlobBuilder = window.BlobBuilder ||
window.WebKitBlobBuilder ||
window.MozBlobBuilder ||
window.MSBlobBuilder;
if(e.name == 'TypeError' && window.BlobBuilder){
var bb = new BlobBuilder();
bb.append(byteArrays);
blob = bb.getBlob(contentType);
}
else if(e.name == "InvalidStateError"){
// InvalidStateError (tested on FF13 WinXP)
blob = new Blob(byteArrays, {type : contentType});
}
else{
// We're screwed, blob constructor unsupported entirely
}
}
For all copy-paste lovers out there like me, here is a cooked download function which works on Chrome, Firefox and Edge:
window.saveFile = function (bytesBase64, mimeType, fileName) {
var fileUrl = "data:" + mimeType + ";base64," + bytesBase64;
fetch(fileUrl)
.then(response => response.blob())
.then(blob => {
var link = window.document.createElement("a");
link.href = window.URL.createObjectURL(blob, { type: mimeType });
link.download = fileName;
document.body.appendChild(link);
link.click();
document.body.removeChild(link);
});
}
I'm posting a more declarative way of sync Base64 converting. While async fetch().blob() is very neat and I like this solution a lot, it doesn't work on Internet Explorer 11 (and probably Edge - I haven't tested this one), even with the polyfill - take a look at my comment to Endless' post for more details.
const blobPdfFromBase64String = base64String => {
const byteArray = Uint8Array.from(
atob(base64String)
.split('')
.map(char => char.charCodeAt(0))
);
return new Blob([byteArray], { type: 'application/pdf' });
};
Bonus
If you want to print it you could do something like:
const isIE11 = !!(window.navigator && window.navigator.msSaveOrOpenBlob); // Or however you want to check it
const printPDF = blob => {
try {
isIE11
? window.navigator.msSaveOrOpenBlob(blob, 'documents.pdf')
: printJS(URL.createObjectURL(blob)); // http://printjs.crabbly.com/
} catch (e) {
throw PDFError;
}
};
Bonus x 2 - Opening a BLOB file in new tab for Internet Explorer 11
If you're able to do some preprocessing of the Base64 string on the server you could expose it under some URL and use the link in printJS :)
For image data, I find it simpler to use canvas.toBlob (asynchronous)
function b64toBlob(b64, onsuccess, onerror) {
var img = new Image();
img.onerror = onerror;
img.onload = function onload() {
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var ctx = canvas.getContext('2d');
ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
canvas.toBlob(onsuccess);
};
img.src = b64;
}
var base64Data = 'data:image/jpg;base64,/9j/4AAQSkZJRgABAQA...';
b64toBlob(base64Data,
function(blob) {
var url = window.URL.createObjectURL(blob);
// do something with url
}, function(error) {
// handle error
});
If you can stand adding one dependency to your project there's the great blob-util npm package that provides a handy base64StringToBlob function. Once added to your package.json you can use it like this:
import { base64StringToBlob } from 'blob-util';
const contentType = 'image/png';
const b64Data = 'iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
const blob = base64StringToBlob(b64Data, contentType);
// Do whatever you need with your blob...
I noticed that Internet Explorer 11 gets incredibly slow when slicing the data like Jeremy suggested. This is true for Chrome, but Internet Explorer seems to have a problem when passing the sliced data to the Blob-Constructor. On my machine, passing 5 MB of data makes Internet Explorer crash and memory consumption is going through the roof. Chrome creates the blob in no time.
Run this code for a comparison:
var byteArrays = [],
megaBytes = 2,
byteArray = new Uint8Array(megaBytes*1024*1024),
block,
blobSlowOnIE, blobFastOnIE,
i;
for (i = 0; i < (megaBytes*1024); i++) {
block = new Uint8Array(1024);
byteArrays.push(block);
}
//debugger;
console.profile("No Slices");
blobSlowOnIE = new Blob(byteArrays, { type: 'text/plain'});
console.profileEnd();
console.profile("Slices");
blobFastOnIE = new Blob([byteArray], { type: 'text/plain'});
console.profileEnd();
So I decided to include both methods described by Jeremy in one function. Credits go to him for this.
function base64toBlob(base64Data, contentType, sliceSize) {
var byteCharacters,
byteArray,
byteNumbers,
blobData,
blob;
contentType = contentType || '';
byteCharacters = atob(base64Data);
// Get BLOB data sliced or not
blobData = sliceSize ? getBlobDataSliced() : getBlobDataAtOnce();
blob = new Blob(blobData, { type: contentType });
return blob;
/*
* Get BLOB data in one slice.
* => Fast in Internet Explorer on new Blob(...)
*/
function getBlobDataAtOnce() {
byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
byteArray = new Uint8Array(byteNumbers);
return [byteArray];
}
/*
* Get BLOB data in multiple slices.
* => Slow in Internet Explorer on new Blob(...)
*/
function getBlobDataSliced() {
var slice,
byteArrays = [];
for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
slice = byteCharacters.slice(offset, offset + sliceSize);
byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
byteArray = new Uint8Array(byteNumbers);
// Add slice
byteArrays.push(byteArray);
}
return byteArrays;
}
}
The method with fetch is the best solution, but if anyone needs to use a method without fetch then here it is, as the ones mentioned previously didn't work for me:
function makeblob(dataURL) {
const BASE64_MARKER = ';base64,';
const parts = dataURL.split(BASE64_MARKER);
const contentType = parts[0].split(':')[1];
const raw = window.atob(parts[1]);
const rawLength = raw.length;
const uInt8Array = new Uint8Array(rawLength);
for (let i = 0; i < rawLength; ++i) {
uInt8Array[i] = raw.charCodeAt(i);
}
return new Blob([uInt8Array], { type: contentType });
}
In browser just
Uint8Array.from(atob(YOUR_BASE64_DATA), (c) => c.charCodeAt(0))
compare with fetch
!(async () => {
const start = performance.now();
let i = 0;
while (i++ < 1e3) {
const dataUrl =
"data:application/octet-stream;base64,H4sIAAAAAAAAA0vOzyvOz0nVy8lP10jISM3JyVdIr8osUFCpdkksSdXLyy/X0KxN0ORKHlU3qm5U3ai6UXWj6kauOgBVt1KRLwcAAA==";
body = await (await fetch(dataUrl)).blob();
}
console.log(performance.now() - start); // 508.19999999925494ms
})();
!(async () => {
const start = performance.now();
let i = 0;
while (i++ < 1e3) {
const base64Data =
"H4sIAAAAAAAAA0vOzyvOz0nVy8lP10jISM3JyVdIr8osUFCpdkksSdXLyy/X0KxN0ORKHlU3qm5U3ai6UXWj6kauOgBVt1KRLwcAAA==";
body = Uint8Array.from(atob(base64Data), (c) => c.charCodeAt(0));
}
console.log(performance.now() - start); // 7.899999998509884ms
})();
Depends on your data size, choose performance one.
Two different variations
function base64ToBlob(base64, contentType='image/png', chunkLength=512) {
const byteCharsArray = Array.from(atob(base64.substr(base64.indexOf(',') + 1)));
const chunksIterator = new Array(Math.ceil(byteCharsArray.length / chunkLength));
const bytesArrays = [];
for (let c = 0; c < chunksIterator.length; c++) {
bytesArrays.push(new Uint8Array(byteCharsArray.slice(c * chunkLength, chunkLength * (c + 1)).map(s => s.charCodeAt(0))));
}
const blob = new Blob(bytesArrays, {type: contentType});
return blob;
}
/* Not sure how it performs with big images */
async function base64ToBlobLight(base64) { return await fetch(base64).then(res => res.blob()); }
/* Test */
const base64Data = 'data:image/png;base64,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';
const blob = base64ToBlob(base64Data);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
/**********************/
/* Test */
(async () => {
const blob = await base64ToBlobLight(base64Data);
const blobUrl = URL.createObjectURL(blob);
const img = document.createElement('img');
img.src = blobUrl;
document.body.appendChild(img);
})();
This would prove to be much short solution.
const byteArray = new Buffer(base64String.replace(/^[\w\d;:\/]+base64\,/g, ''), 'base64');
base64String is the string containing the base 64 string.
byteArray is the array you need.
The regex replacement is optional and is just there to deal with prefix as in the case of dataurl string.
My problem:
I'm trying to merge multiple blob audio files to a single blob and download it on the page.
What I tried:
I tried to concatenate the Audio blobs in the following ways:
Method - 1:
const url = window.URL.createObjectURL(new Blob(fullBlobArray), {
type: 'audio/*'
});
const a = document.createElement("a");
document.body.appendChild(a);
a.style = "display: none";
a.href = url;
a.download = "testing.wav";
a.click();
URL.revokeObjectURL(url);
a.remove();
Method - 2 (Using - ConcatenateBlobs.js plugin - ConcatenateJS)
ConcatenateBlobs(fullBlobArray, 'audio/wav', function (fullBlob) {
const url = window.URL.createObjectURL(fullBlob);
const a = document.createElement("a");
document.body.appendChild(a);
a.style = "display: none";
a.href = url;
a.download = "testing.wav";
a.click();
URL.revokeObjectURL(url);
a.remove();
//Close the window if it downloaded.
window.close();
Output is explained below:
If you have the following audio blobs:
[audio1, audio2, audio3]
Then, after downloading from the above code, only the Audio from the first file (i.e. audio1 ) is getting played. But the file size of the full blob is the total size of audio1 + audio2 + audio3
I couldn't figure out where I went wrong. Kindly help me in this to get rid of this problem.
Finally, found a solution!!!
Thanks for this StackOverflow article. Highly appreciated for the efforts for this article.
Thanks for the commenting out (#Bergi, #Zac, #Peter Krebs in the comments) that we need to Format the blob according to WAV Format
For merging multiple WAV files into a single file and below is the code:
wav_merger.js
var _index;
function readFileAsync(blob) {
return new Promise((resolve, reject) => {
let reader = new FileReader();
reader.addEventListener("loadend", function () {
resolve(reader.result);
});
reader.onerror = reject;
reader.readAsArrayBuffer(blob);
})
}
function getBufferFromBlobs(blobArray) {
return new Promise((resolve, reject) => {
var _arrBytes = [];
var _promises = [];
if (blobArray.length > 0) {
$.each(blobArray, function (index, blob) {
_index = index;
var dfd = $.Deferred();
readFileAsync(blob).then(function (byteArray) {
_arrBytes.push(byteArray);
dfd.resolve();
});
_promises.push(dfd);
});
$.when.apply($, _promises).done(function () {
var _blob = combineWavsBuffers(_arrBytes);
resolve(_blob);
});
}
});
}
function loadWav(blobArray) {
return getBufferFromBlobs(blobArray);
debugger;
// .then(function (bufferArray) {
// return combineWavsBuffers(bufferArray); //Combine original wav buffer and play
//});
}
function combineWavsBuffers(bufferArray) {
if (bufferArray.length > 0) {
var _bufferLengths = bufferArray.map(buffer => buffer.byteLength);
// Getting sum of numbers
var _totalBufferLength = _bufferLengths.reduce(function (a, b) {
return a + b;
}, 0);
var tmp = new Uint8Array(_totalBufferLength);
//Get buffer1 audio data to create the new combined wav
var audioData = getAudioData.WavHeader.readHeader(new DataView(bufferArray[0]));
var _bufferLength = 0;
$.each(bufferArray, function (index, buffer) {
//Combine array bytes of original wavs buffers.
tmp.set(new Uint8Array(buffer), _bufferLength);
_bufferLength+= buffer.byteLength;
});
//Send combined buffer and send audio data to create the audio data of combined
var arrBytesFinal = getWavBytes(tmp, {
isFloat: false, // floating point or 16-bit integer
numChannels: audioData.channels,
sampleRate: audioData.sampleRate,
});
//Create a Blob as Base64 Raw data with audio/wav type
return new Blob([arrBytesFinal], { type: 'audio/wav; codecs=MS_PCM' });
}
return null;
}
//Combine two audio .wav buffers.
function combineWavsBuffers1(buffer1, buffer2) {
//Combine array bytes of original wavs buffers
var tmp = new Uint8Array(buffer1.byteLength + buffer2.byteLength);
tmp.set(new Uint8Array(buffer1), 0);
tmp.set(new Uint8Array(buffer2), buffer1.byteLength);
//Get buffer1 audio data to create the new combined wav
var audioData = getAudioData.WavHeader.readHeader(new DataView(buffer1));
console.log('Audio Data: ', audioData);
//Send combined buffer and send audio data to create the audio data of combined
var arrBytesFinal = getWavBytes(tmp, {
isFloat: false, // floating point or 16-bit integer
numChannels: audioData.channels,
sampleRate: audioData.sampleRate,
});
//Create a Blob as Base64 Raw data with audio/wav type
return new Blob([arrBytesFinal], { type: 'audio/wav; codecs=MS_PCM' });
}
//Other functions //////////////////////////////////////////////////////////////
// Returns Uint8Array of WAV bytes
function getWavBytes(buffer, options) {
const type = options.isFloat ? Float32Array : Uint16Array
const numFrames = buffer.byteLength / type.BYTES_PER_ELEMENT
const headerBytes = getWavHeader(Object.assign({}, options, { numFrames }))
const wavBytes = new Uint8Array(headerBytes.length + buffer.byteLength);
// prepend header, then add pcmBytes
wavBytes.set(headerBytes, 0)
wavBytes.set(new Uint8Array(buffer), headerBytes.length)
return wavBytes
}
// adapted from https://gist.github.com/also/900023
// returns Uint8Array of WAV header bytes
function getWavHeader(options) {
const numFrames = options.numFrames
const numChannels = options.numChannels || 2
const sampleRate = options.sampleRate || 44100
const bytesPerSample = options.isFloat ? 4 : 2
const format = options.isFloat ? 3 : 1
const blockAlign = numChannels * bytesPerSample
const byteRate = sampleRate * blockAlign
const dataSize = numFrames * blockAlign
const buffer = new ArrayBuffer(44)
const dv = new DataView(buffer)
let p = 0
function writeString(s) {
for (let i = 0; i < s.length; i++) {
dv.setUint8(p + i, s.charCodeAt(i))
}
p += s.length
}
function writeUint32(d) {
dv.setUint32(p, d, true)
p += 4
}
function writeUint16(d) {
dv.setUint16(p, d, true)
p += 2
}
writeString('RIFF') // ChunkID
writeUint32(dataSize + 36) // ChunkSize
writeString('WAVE') // Format
writeString('fmt ') // Subchunk1ID
writeUint32(16) // Subchunk1Size
writeUint16(format) // AudioFormat
writeUint16(numChannels) // NumChannels
writeUint32(sampleRate) // SampleRate
writeUint32(byteRate) // ByteRate
writeUint16(blockAlign) // BlockAlign
writeUint16(bytesPerSample * 8) // BitsPerSample
writeString('data') // Subchunk2ID
writeUint32(dataSize) // Subchunk2Size
return new Uint8Array(buffer)
}
function getAudioData() {
function WavHeader() {
this.dataOffset = 0;
this.dataLen = 0;
this.channels = 0;
this.sampleRate = 0;
}
function fourccToInt(fourcc) {
return fourcc.charCodeAt(0) << 24 | fourcc.charCodeAt(1) << 16 | fourcc.charCodeAt(2) << 8 | fourcc.charCodeAt(3);
}
WavHeader.RIFF = fourccToInt("RIFF");
WavHeader.WAVE = fourccToInt("WAVE");
WavHeader.fmt_ = fourccToInt("fmt ");
WavHeader.data = fourccToInt("data");
WavHeader.readHeader = function (dataView) {
var w = new WavHeader();
var header = dataView.getUint32(0, false);
if (WavHeader.RIFF != header) {
return;
}
var fileLen = dataView.getUint32(4, true);
if (WavHeader.WAVE != dataView.getUint32(8, false)) {
return;
}
if (WavHeader.fmt_ != dataView.getUint32(12, false)) {
return;
}
var fmtLen = dataView.getUint32(16, true);
var pos = 16 + 4;
switch (fmtLen) {
case 16:
case 18:
w.channels = dataView.getUint16(pos + 2, true);
w.sampleRate = dataView.getUint32(pos + 4, true);
break;
default:
throw 'extended fmt chunk not implemented';
}
pos += fmtLen;
var data = WavHeader.data;
var len = 0;
while (data != header) {
header = dataView.getUint32(pos, false);
len = dataView.getUint32(pos + 4, true);
if (data == header) {
break;
}
pos += (len + 8);
}
w.dataLen = len;
w.dataOffset = pos + 8;
return w;
};
getAudioData.WavHeader = WavHeader;
}
getAudioData();
custom_script.js
getBufferFromBlobs(fullBlobArray).then(function (singleBlob) {
const url = window.URL.createObjectURL(singleBlob);
const a = document.createElement("a");
document.body.appendChild(a);
a.style = "display: none";
a.href = url;
a.download = "testing.wav";
a.click();
URL.revokeObjectURL(url);
a.remove();
});
Have the same problem, thank #Vikash to bring it here. I'm using ConcatenateBlobs.js to concat wav blobs and it seems only working on Chrome. Your solution is great but the source is a bit long, so I tried to fix ConcatenateBlobs.js base on the fact that file length in the header need to be fixed. Luckily, it works:
function ConcatenateBlobs(blobs, type, callback) {
var buffers = [];
var index = 0;
function readAsArrayBuffer() {
if (!blobs[index]) {
return concatenateBuffers();
}
var reader = new FileReader();
reader.onload = function(event) {
buffers.push(event.target.result);
index++;
readAsArrayBuffer();
};
reader.readAsArrayBuffer(blobs[index]);
}
readAsArrayBuffer();
function audioLengthTo32Bit(n) {
n = Math.floor(n);
var b1 = n & 255;
var b2 = (n >> 8) & 255;
var b3 = (n >> 16) & 255;
var b4 = (n >> 24) & 255;
return [b1, b2, b3, b4];
}
function concatenateBuffers() {
var byteLength = 0;
buffers.forEach(function(buffer) {
byteLength += buffer.byteLength;
});
var tmp = new Uint8Array(byteLength);
var lastOffset = 0;
var newData;
buffers.forEach(function(buffer) {
if (type=='audio/wav' && lastOffset > 0) newData = new Uint8Array(buffer, 44);
else newData = new Uint8Array(buffer);
tmp.set(newData, lastOffset);
lastOffset += newData.length;
});
if (type=='audio/wav') {
tmp.set(audioLengthTo32Bit(lastOffset - 8), 4);
tmp.set(audioLengthTo32Bit(lastOffset - 44), 40); // update audio length in the header
}
var blob = new Blob([tmp.buffer], {
type: type
});
callback(blob);
}
}
I am getting base64 string from node JavaScript back-end. But it is not working like Chrome.
I can't find any solutions in web. Getting 200 status in API call but it is not downloading file in Firefox while same code working fine with Chrome.
Here is my code::
static downloadFile(fileName: string, fileMimeType: string, uri: string) {
const dataURI = uri;
const blob = this.dataURIToBlob(dataURI);
const url = URL.createObjectURL(blob);
const blobAnchor = document.createElement('a');
const dataURIAnchor = document.createElement('a');
blobAnchor.download = dataURIAnchor.download = fileName;
blobAnchor.href = url;
dataURIAnchor.href = dataURI;
blobAnchor.onclick = function () {
requestAnimationFrame(function () {
URL.revokeObjectURL(url);
});
};
blobAnchor.click();
}
static dataURIToBlob(dataURI) {
const binStr = atob(dataURI.split(',')[1]),
len = binStr.length,
arr = new Uint8Array(len),
mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
for (let i = 0; i < len; i++) {
arr[i] = binStr.charCodeAt(i);
}
return new Blob([arr], {
type: mimeString
});
}
I am getting all the data from Node.js and working fine with Chrome. So I can't find any issue why it is not working with Firefox.
In firefox you have to append your a into DOM and then perform click.
Used document.body.appendChild(blobAnchor); to append into DOM.
Added blobAnchor.className = 'hidden'; so it will not be visible.
And removed from DOM after few seconds with setTimeout(() => blobAnchor.remove(), 300);.
static downloadFile(fileName: string, fileMimeType: string, uri: string) {
const dataURI = uri;
const blob = this.dataURIToBlob(dataURI);
const url = URL.createObjectURL(blob);
const blobAnchor = document.createElement('a');
const dataURIAnchor = document.createElement('a');
blobAnchor.download = dataURIAnchor.download = fileName;
blobAnchor.className = 'hidden';
blobAnchor.href = url;
dataURIAnchor.href = dataURI;
document.body.appendChild(blobAnchor);
blobAnchor.onclick = function () {
requestAnimationFrame(function () {
URL.revokeObjectURL(url);
setTimeout(() => blobAnchor.remove(), 300);
});
};
blobAnchor.click();
}
static dataURIToBlob(dataURI) {
const binStr = atob(dataURI.split(',')[1]),
len = binStr.length,
arr = new Uint8Array(len),
mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
for (let i = 0; i < len; i++) {
arr[i] = binStr.charCodeAt(i);
}
return new Blob([arr], {
type: mimeString
});
}
I am creating an image editor which I am using for editing image before uploading.
So for this, I am using cropper JS.
but here is some problem, Image's size increases after editing image.
So, I want to maintain the quality of the image after editing it as of original image have.
here is som
private getImageFromBase64(file: File, base64, callback) {
let dataURI = base64;
let typeOfImage = file.type;
let nameOfImage = file.name;
// convert base64 to raw binary data held in a string
let byteString = atob(dataURI.split(',')[1]);
// separate out the mime component
let mimeString = dataURI
.split(',')[0]
.split(':')[1]
.split(';')[0];
// write the bytes of the string to an ArrayBuffer
let ab = new ArrayBuffer(byteString.length);
let ia = new Uint8Array(ab);
for (let i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
// write the ArrayBuffer to a blob, and you're done
let bb: Blob = new Blob([ab], { type: typeOfImage });
let editedFile: any;
try {
editedFile = new File([bb], nameOfImage, { type: typeOfImage });
} catch (err) {
editedFile = bb;
editedFile.name = nameOfImage;
editedFile.lastModifiedDate = new Date();
}
return callback(editedFile);
}
private save(cb) {
let result = this.cropper.getCroppedCanvas({
width: this.width || 600,
height: this.height || 858
});
try {
result.toBlob((blob: any) => {
blob.name = this.file.name;
blob.lastModifiedDate = new Date();
cb(blob);
});
} catch (err) {
this.getImageFromBase64(this.file, result.toDataURL('jpeg', 0.8), cb);
}
}