How to convert a base64 string into a file? - javascript

I used a jquery plugin to crop images. The plugin will crop the image and give it to me as a base64 encoded string. In order to upload it to S3, I need to convert this into a file and pass the file into the upload function. How can I do this? I tried a lot of things including decoding the string using atob. None worked.
Here's the code of the cropping plugin ('croppie') which gives me the encoded string :
imageCropper.croppie('result', {
type: 'canvas',
size: 'viewport',
format: 'jpeg'
}).then(function (resp) {
updateAvatar(resp);
});
I pass it to a function called updateAvatar. Here's the updateAvatar function :
updateAvatar({Meteor, Slingshot}, avatar) {
const uploader = new Slingshot.Upload('userAvatarUpload');
uploader.send(avatar, function (error, downloadUrl) {
if (error) {
// Log service detailed response.
console.error('Error uploading', uploader.xhr.response);
console.log(error);
}
else {
console.log('uploaded', downloadUrl);
}
});
}
The uploader.send function expects a file or a url. It won't accept my encoded string.
The plugin which I use to upload files to S3 : https://github.com/CulturalMe/meteor-slingshot

It seems like the missing 'brick' in your code is a function that would take a base64-encoded image and convert it to a Blob.
So, I'm going to focus on that part exclusively with a short comment for each step.
The following function expects a string such as:
data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAMCAgICA...
function base64ImageToBlob(str) {
// extract content type and base64 payload from original string
var pos = str.indexOf(';base64,');
var type = str.substring(5, pos);
var b64 = str.substr(pos + 8);
// decode base64
var imageContent = atob(b64);
// create an ArrayBuffer and a view (as unsigned 8-bit)
var buffer = new ArrayBuffer(imageContent.length);
var view = new Uint8Array(buffer);
// fill the view, using the decoded base64
for(var n = 0; n < imageContent.length; n++) {
view[n] = imageContent.charCodeAt(n);
}
// convert ArrayBuffer to Blob
var blob = new Blob([buffer], { type: type });
return blob;
}

Convert the base64 string to blob, to be used in upload to S3. There are tidier ways of doing this of course! :)
Original SO Answer here: https://stackoverflow.com/a/16245768/1350913
imageCropper.croppie('result', {
type: 'canvas',
size: 'viewport',
format: 'jpeg'
}).then(function(resp) {
var contentType = 'image/png';
var s3Blob = b64toBlob(resp, contentType);
updateAvatar(s3Blob);
});
updateAvatar({
Meteor,
Slingshot
}, avatar) {
const uploader = new Slingshot.Upload('userAvatarUpload');
uploader.send(avatar, function(error, downloadUrl) {
if (error) {
// Log service detailed response.
console.error('Error uploading', uploader.xhr.response);
console.log(error);
} else {
console.log('uploaded', downloadUrl);
}
});
}
function b64toBlob(b64Data, contentType, sliceSize) {
contentType = contentType || '';
sliceSize = sliceSize || 512;
var b64DataString = b64Data.substr(b64Data.indexOf(',') + 1);
var byteCharacters = atob(b64DataString);
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;
}

The base64ToFile function (.ts) converts the base64 string into a File. The codeUnits and charCodes part make sure you can read Unicode text as ASCII by converting the string such that each 16-bit unit occupies only one byte.
Finally the download function (.ts) downloads the converted file from your browser to your local machine.
function base64ToFile(base64data: string, myFileNameWithdotExtention: string,
fileType: string): File {
let content = decodeURIComponent(escape(window.atob(base64data)));
let fileName = myFileNameWithdotExtention;
const codeUnits = Uint16Array.from(
{ length: content.length },
( _, index) => content.charCodeAt(index)
);
const charCodes = new Uint8Array(codeUnits.buffer);
const type = fileType; // 'text/csv' for instance
const blob = new Blob([charCodes], { type });
return new File([blob], fileName, { lastModified: new Date().getTime(), type });
}
download(){
let res: string = getMyDataFromSomewhere(); // base64 string
let data = base64ToFile(res);
let element = document.createElement('a');
window.URL = window.URL || window.webkitURL;
element.setAttribute('href', window.URL.createObjectURL(data));
element.setAttribute('download', data.name);
element.style.display = 'none';
document.body.appendChild(element);
element.click();
document.body.removeChild(element);
}

Related

I have base64 stream of a pdf file. Now I need to convert it into a pdf file in Native Javascript. How can I do that? [duplicate]

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,iVBORw0KGgoAAAANSUhEUgAAABgAAAAYCAMAAADXqc3KAAAB+FBMVEUAAAA/mUPidDHiLi5Cn0XkNTPmeUrkdUg/m0Q0pEfcpSbwaVdKskg+lUP4zA/iLi3msSHkOjVAmETdJSjtYFE/lkPnRj3sWUs8kkLeqCVIq0fxvhXqUkbVmSjwa1n1yBLepyX1xxP0xRXqUkboST9KukpHpUbuvRrzrhF/ljbwaljuZFM4jELaoSdLtElJrUj1xxP6zwzfqSU4i0HYnydMtUlIqUfywxb60AxZqEXaoifgMCXptR9MtklHpEY2iUHWnSjvvRr70QujkC+pUC/90glMuEnlOjVMt0j70QriLS1LtEnnRj3qUUXfIidOjsxAhcZFo0bjNDH0xxNLr0dIrUdmntVTkMoyfL8jcLBRuErhJyrgKyb4zA/5zg3tYFBBmUTmQTnhMinruBzvvhnxwxZ/st+Ktt5zp9hqota2vtK6y9FemNBblc9HiMiTtMbFtsM6gcPV2r6dwroseLrMrbQrdLGdyKoobKbo3Zh+ynrgVllZulTsXE3rV0pIqUf42UVUo0JyjEHoS0HmsiHRGR/lmRz/1hjqnxjvpRWfwtOhusaz0LRGf7FEfbDVmqHXlJeW0pbXq5bec3fX0nTnzmuJuWvhoFFhm0FtrziBsjaAaDCYWC+uSi6jQS3FsSfLJiTirCOkuCG1KiG+wSC+GBvgyhTszQ64Z77KAAAARXRSTlMAIQRDLyUgCwsE6ebm5ubg2dLR0byXl4FDQzU1NDEuLSUgC+vr6urq6ubb29vb2tra2tG8vLu7u7uXl5eXgYGBgYGBLiUALabIAAABsElEQVQoz12S9VPjQBxHt8VaOA6HE+AOzv1wd7pJk5I2adpCC7RUcHd3d3fXf5PvLkxheD++z+yb7GSRlwD/+Hj/APQCZWxM5M+goF+RMbHK594v+tPoiN1uHxkt+xzt9+R9wnRTZZQpXQ0T5uP1IQxToyOAZiQu5HEpjeA4SWIoksRxNiGC1tRZJ4LNxgHgnU5nJZBDvuDdl8lzQRBsQ+s9PZt7s7Pz8wsL39/DkIfZ4xlB2Gqsq62ta9oxVlVrNZpihFRpGO9fzQw1ms0NDWZz07iGkJmIFH8xxkc3a/WWlubmFkv9AB2SEpDvKxbjidN2faseaNV3zoHXvv7wMODJdkOHAegweAfFPx4G67KluxzottCU9n8CUqXzcIQdXOytAHqXxomvykhEKN9EFutG22p//0rbNvHVxiJywa8yS2KDfV1dfbu31H8jF1RHiTKtWYeHxUvq3bn0pyjCRaiRU6aDO+gb3aEfEeVNsDgm8zzLy9egPa7Qt8TSJdwhjplk06HH43ZNJ3s91KKCHQ5x4sw1fRGYDZ0n1L4FKb9/BP5JLYxToheoFCVxz57PPS8UhhEpLBVeAAAAAElFTkSuQmCC';
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.

Getting corrupted file while exporting .xls file using java/javascript and apache POI

I am trying to downlaod a .xls file in browser from a web application. Below is the code for the same.
try(FileInputStream inputStream = new FileInputStream("C:\\Users\\Desktop\\Book1.xls")){
response.setContentType("application/vnd.ms-excel");
//response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
response.setHeader("Content-Disposition", "attachment; filename=Book1.xls");
outputStream = response.getOutputStream();
byte[] buffer = new byte[BUFFERSIZE];
int bytesRead = -1;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
}
Below is the javascript code used to download the file content.
success: function(response, status, xhr) {
let type = xhr.getResponseHeader('Content-Type');
let blob = new Blob([response], { type: type });
if (typeof window.navigator.msSaveBlob !== 'undefined') {
// IE workaround for "HTML7007: One or more blob URLs were revoked by closing the blob for which they were created.
//These URLs will no longer resolve as the data backing the URL has been freed."
window.navigator.msSaveBlob(blob, filename);
} else {
let URL = window.URL || window.webkitURL;
let downloadUrl = URL.createObjectURL(blob);
if (filename) {
// use HTML5 a[download] attribute to specify filename
let a = document.createElement("a");
// safari doesn't support this yet
if (typeof a.download === 'undefined') {
window.location = downloadUrl;
} else {
a.href = downloadUrl;
a.download = filename;
document.body.appendChild(a);
a.click();
}
} else {
window.location = downloadUrl;
}
setTimeout(function () {
URL.revokeObjectURL(downloadUrl);
}, 100); // cleanup
}
}
I am able to download the file, but downloaded file content is not in readble format. If it is csv file I am able to see content in my javascript response object where as for .xls file javascript response object contains unreadable formatted data.
Can somebody help me here?
Posting this solution if anyone else faces the same issue, I resolved this issue via base64 encoding the byte array to a string as below.
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
workbook.write(outputStream);
String res = Base64.getEncoder().encodeToString(outputStream.toByteArray());
In javascript I decoded that string using base64ToBlob method from below link
https://stackoverflow.com/a/20151856/2011294
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 });
}

Error when printing PDF file in AngularJS

I am trying to print a PDF file generated through reportViewer in my Web API, but the browser shows an error when tries to open the PDF file.
This is the code inside the controller in my Web API:
// ...generate candidatosDataSet
LocalReport relatorio = new LocalReport();
string rootPath = HttpRuntime.AppDomainAppPath;
relatorio.ReportPath = rootPath + #"\Reports\Report.rdlc";
relatorio.DataSources.Add(new ReportDataSource("Candidatos", candidatosDataSet));
relatorio.Refresh();
byte[] relatorioBytes = ExportUtils.GerarArquivoPDF(relatorio);
response = Request.CreateResponse(HttpStatusCode.OK, relatorioBytes);
response.Content.Headers.ContentDisposition = System.Net.Http.Headers.ContentDispositionHeaderValue.Parse("attachment; filename=relatorio.pdf");
response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/pdf");
This is how I am generating PDF File through reportViewer
public static byte[] GerarArquivoPDF(LocalReport relatorio)
{
String reportType = "PDF";
String mimeType;
String encoding;
String fileNameExtension;
String deviceInfo;
Warning[] warnings;
string[] streams;
byte[] renderedBytes;
deviceInfo = "<DeviceInfo>" + " <OutputFormat>" + reportType + "</OutputFormat>" + "</DeviceInfo>";
renderedBytes = relatorio.Render(
reportType,
deviceInfo,
out mimeType,
out encoding,
out fileNameExtension,
out streams,
out warnings);
return renderedBytes;
}
Here is my AngularJS service method:
function obterTermoConfirmacaoCandidatura(candidatoId) {
return $http.get(configValues.baseUrl + 'candidato/GetRelatorio',
{
params: { candidatoId: candidatoId },
responseType: 'arraybuffer'
});
}
And this is the code that I am using to print the file on the AngularJS controller:
function imprimirTermoConfirmacaoCandidatura(id) {
CandidatoAPIService.obterTermoConfirmacaoCandidatura(id)
.then(function (response) {
var contentType = response.headers('Content-Type') || "application/octet-stream";
var file = new Blob([response.data], {
type: contentType
});
var fileUrl = URL.createObjectURL(file);
var printWindow = $window.open(fileUrl);
printWindow.print();
}, function (error) {
alert(error.data);
});
}
The response from Web API was comming as string, with double quotes in beginning and in the end of the response, so the PDF File could not be rendered correctly. Also I converted the response from server to base64, by this method:
function b64toBlob(b64Data, contentType) {
var sliceSize = 512;
b64Data = b64Data.replace(/"/g, '');
b64Data = b64Data.replace(/^[^,]+,/, '');
b64Data = b64Data.replace(/\s/g, '');
var byteCharacters = window.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;
}
And changed the method on AngularJS controller to convert the response do base64:
function imprimirTermoAutorizacaoUsoImagem() {
CandidatoAPIService.obterTermoAutorizacaoUsoImagem()
.then(function (response) {
var contentType = response.headers('Content-Type') || "application/octet-stream";
var file = UtilsService.b64toBlob(response.data, "application/pdf");
var fileUrl = URL.createObjectURL(file);
var printWindow = $window.open(fileUrl);
printWindow.print();
}, function (error) {
alert(error.data);
});
}
And removed the responseType on the AngularJS service:
function obterTermoConfirmacaoCandidatura(candidatoId) {
return $http.get(configValues.baseUrl + 'candidato/GetObterTermoConfirmacaoCandidatura',
{
params: { candidatoId: candidatoId }
});
}

Return base64 String of a File as a response using ASP.NET httpHandler inresponse to AJAX Request

I want to download multiple types of files using AJAX.
I decided to generate a get requests with file name as query string using AJAX and get the response as base64 string and then convert it to blob object and download/save it using hyperlink a tag along with download attribute.
Kindly help me, how to use the optimized way/code to convert file to base64 string and then revert the base64 string to blob?
ASP.Net httpHandler code is here:
Imports System
Imports System.Web
Imports System.IO
Public Class FileDownload : Implements IHttpHandler
Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
Dim Request As HttpRequest = context.Request
Dim Response As HttpResponse = context.Response
Dim serverFile As String = Request.QueryString("filename")
Dim filePath As String = String.Empty
filePath = context.Server.MapPath("~") & "\" & serverFile
Dim file As New System.IO.FileInfo(filePath)
Try
If (file.Exists) Then
Response.Clear()
Response.ClearContent()
Using reader As New FileStream(filePath, FileMode.Open, IO.FileAccess.Read, IO.FileShare.Read)
Dim buffer As Byte() = New Byte(reader.Length - 1) {}
reader.Read(buffer, 0, CInt(reader.Length))
Response.Write(Convert.ToBase64String(buffer))
End Using
Response.Flush()
Response.End()
Else
Response.Write("File Not Found!")
Response.StatusCode = 500
End If
Catch ex As Exception
Response.Write(ex.ToString)
Response.StatusCode = 500
context.ApplicationInstance.CompleteRequest()
End Try
End Sub
Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
Get
Return False
End Get
End Property
End Class
Javascript function called with httphadler's application path as url and client side file name as filename
function downloadFileByAjax(filename, url) {
$.ajax({
type: 'GET',
url: url,
responseType: 'arraybuffer',
downloadid: filename,
success: function (result, status, xhr) {
var octetStreamMime = 'application/octet-stream';
var filename = this.downloadid;
var contentType = xhr.getResponseHeader('content-type') || octetStreamMime;
var a = document.createElement('a');
var urlCreator = window.URL || window.webkitURL || window.mozURL || window.msURL;
if (urlCreator && window.Blob && ('download' in a) && window.atob) {
var blob = base64ToBlob(result, contentType);
var url = window.URL.createObjectURL(blob);
a.setAttribute('href', url);
a.setAttribute("download", filename);
var event = document.createEvent('MouseEvents');
event.initMouseEvent('click', true, true, window, 1, 0, 0, 0, 0, false, false, false, false, 0, null);
a.dispatchEvent(event);
//window.URL.revokeObjectURL(url);
}
},
error: function (xhr, msg, error) {
//console.log(xhr, msg, error);
//console.log(xhr.responseText);
console.log(msg);
},
complete: function (xhr, status) {
//console.log('completed');
}
});
}
function base64ToBlob(base64, mimetype, slicesize) {
if (!window.atob || !window.Uint8Array) {
console.log('The current browser doesnot have the atob function. Cannot continue');
return null;
}
mimetype = mimetype || '';
slicesize = slicesize || 512;
var bytechars = atob(base64);
var bytearrays = [];
for (var offset = 0; offset < bytechars.length; offset += slicesize) {
var slice = bytechars.slice(offset, offset + slicesize);
var bytenums = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
bytenums[i] = slice.charCodeAt(i);
}
var bytearray = new Uint8Array(bytenums);
bytearrays[bytearrays.length] = bytearray;
}
return new Blob(bytearrays, { type: mimetype });
}
To convert a file to base64 string use the following code
string data;
using (FileStream fs = new FileStream(dir + fileName, FileMode.Open, FileAccess.Read)) {
byte[] buffer = new byte[fs.Length];
fs.Read(buffer, 0, (int)fs.Length);
data = Convert.ToBase64String(buffer);
fs.Close();
}
return data;
In the success function of the ajax call convert the string to blob using the following code
var byteCharacters = atob(data);
var byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
var blob = null;
blob = new Blob([byteArray], { type: 'text/plain' });
blob = new Blob([byteArray], { type: 'application/pdf;base64' });
var blobUrl = URL.createObjectURL(blob);
Depending upon the file format you can specify the type attribute for the blob and then assign the blobUrl as the source to your anchor tag

Create a file with data ur

I have something like this.
"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAKQAAACkCAYAAAAZtYVBAAAgAElEQ…TFHIWRhe2sii/S5zA+N/ZF6gI+RiSKspPUBiI1UQf9/wDVxYvlSggfZqgAAAABJRU5Erkaa==="
Is there a way to create a file object? with this?
i see the method URL.createObjectURl but it seems like a need to create a blobl object and i dont really know how.
The following function will convert a data URI to a blob.
function dataURIToBlob(dataURI) {
// Split the dataUri up into parts
// data:[<mediatype>][;<charset>],(data)
var parts = /data:([^;]+)(?:;([^,]+))?,(.+)/.exec(dataURI),
mime = parts[1],
charset = parts[2] || 'charset=US-ASCII',
encodedData = parts[3];
var data;
if (charset === 'base64') {
// If base64 convert to a Uint8 clamped array of character codes
var decodedData = atob(encodedData);
data = new Uint8Array(decodedData.length);
for (var i = 0; i < decodedData.length; i++) {
data[i] = decodedData.charCodeAt(i);
}
} else {
data = decodeURIComponent(encodedData);
}
return new Blob([data], {
type: mime
});
}
You can see it working in this snippet which takes a data URI, converts it into a blob, then creates a blob URI that you can use to access the file. A sample image and CSV file is provided.
testData = {};
testData['image/gif'] = 'data:image/gif;base64,R0lGODlhEAAQAMQAAORHHOVSKudfOulrSOp3WOyDZu6QdvCchPGolfO0o/XBs/fNwfjZ0frl3/zy7////wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACH5BAkAABAALAAAAAAQABAAAAVVICSOZGlCQAosJ6mu7fiyZeKqNKToQGDsM8hBADgUXoGAiqhSvp5QAnQKGIgUhwFUYLCVDFCrKUE1lBavAViFIDlTImbKC5Gm2hB0SlBCBMQiB0UjIQA7';
testData['text/csv'] = 'data:text/csv;charset=utf-8,ID%2CScore%2CAssignee%2CCreated%2CComment%0Aid_value0%2Cscore_value0%2Cassignee_value0%2Ccreated_value0%2Ccomment_value0%0Aid_value1%2Cscore_value1%2Cassignee_value1%2Ccreated_value1%2Ccomment_value1%0Aid_value2%2Cscore_value2%2Cassignee_value2%2Ccreated_value2%2Ccomment_value2%0A';
function dataURIToBlob(dataURI) {
// Split the dataUri up into parts
// data:[<mediatype>][;<charset>],(data)
var parts = /data:([^;]+)(?:;([^,]+))?,(.+)/.exec(dataURI),
mime = parts[1],
charset = parts[2] || 'charset=US-ASCII',
encodedData = parts[3];
var data;
if (charset === 'base64') {
// If base64 convert to a Uint8 clamped array of character codes
var decodedData = atob(encodedData);
data = new Uint8Array(decodedData.length);
for (var i = 0; i < decodedData.length; i++) {
data[i] = decodedData.charCodeAt(i);
}
} else {
data = decodeURIComponent(encodedData);
}
return new Blob([data], {
type: mime
});
}
function createBlobURI() {
var blob = dataURIToBlob(dataURIInput.value);
var blobURI = URL.createObjectURL(blob);
blobURIAnchor.href = blobURI;
blobURIAnchor.innerHTML = blobURI;
blobURIAnchor.style.display = 'block';
blobURIAnchor.download = 'blob.' + blob.type.split('/')[1];
}
function insertTestData(mime) {
dataURIInput.value = testData[mime];
}
insertTestData('image/gif');
<button onclick="insertTestData('image/gif')">Image test</button>
<button onclick="insertTestData('text/csv')">CSV test</button>
<input id="dataURIInput" type="text"/>
<button onclick='createBlobURI()'>Create blob URI</button>
<a id="blobURIAnchor" href="#" style="display:none"></a>

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