HTML5 / Javascript - DataURL to Blob & Blob to DataURL - javascript

I have a DataURL from a canvas that shows my webcam. I turn this dataURL into a blob using Matt's answer from here: How to convert dataURL to file object in javascript?
How do I convert this blob back into the same DataURL? I've spent a day researching this and I'm astouned this isn't documented better, unless I'm blind.
EDIT:
There is
var urlCreator = window.URL || window.webkitURL;
var imageUrl = urlCreator.createObjectURL(blob);
but it only returns a really short URL that seems to point at a local file, but I need to send the webcam data over a network.


Use my code to convert between dataURL and blob object in javascript. (better than the code in your link.)
//**dataURL to blob**
function dataURLtoBlob(dataurl) {
var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],
bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
while(n--){
u8arr[n] = bstr.charCodeAt(n);
}
return new Blob([u8arr], {type:mime});
}
//**blob to dataURL**
function blobToDataURL(blob, callback) {
var a = new FileReader();
a.onload = function(e) {callback(e.target.result);}
a.readAsDataURL(blob);
}
//test:
var blob = dataURLtoBlob('data:text/plain;base64,YWFhYWFhYQ==');
blobToDataURL(blob, function(dataurl){
console.log(dataurl);
});


Here is a Promise-based Typescript version with proper error checking.
function blobToDataURL(blob: Blob): Promise<string> {
return new Promise<string>((resolve, reject) => {
const reader = new FileReader();
reader.onload = _e => resolve(reader.result as string);
reader.onerror = _e => reject(reader.error);
reader.onabort = _e => reject(new Error("Read aborted"));
reader.readAsDataURL(blob);
});
}


Nevermind, it ended up working after sticking to the instructions in this thread Display image from blob using javascript and websockets and making my server forward raw (yet) unmodified BinaryWebSocketFrames.
Now I'm still fighting bad performance of the canvas (<1fp) but that might become subject of a new thread.


I like one-liners, so here's a Promise-based one to convert a blob to a data URL:
let blob = ...;
let dataUrl = await new Promise(r => {let a=new FileReader(); a.onload=r; a.readAsDataURL(blob)}).then(e => e.target.result);
Or, as a function:
function blobToDataUrl(blob) {
return new Promise(r => {let a=new FileReader(); a.onload=r; a.readAsDataURL(blob)}).then(e => e.target.result);
}
let dataUrl = await blobToDataUrl(blob);


DataURL to Blob has a better solution:
const dataURL = "dataURL string...";
const res = await fetch(dataURL);
const blob = await res.blob();

Related

Getting the binary content of a BLOB

I know that, in order to convert a BLOB object to a readable format (URL) in Javascript, I should use the createObjectURL() method, right ?
Example :
var blob = new Blob(["Example"], { type: "text/plain" });
url = window.URL.createObjectURL(blob);
My question is:
Is it possible to get the raw binary content of a BLOB ? so, I can get something like :
"01000101 01111000 01100001 01101101 01110000 01101100 01100101" // "Example" in binary .

Convert the blob to an ArrayBuffer (see 2 methods). Create an ArrayBufferView (Int8array in this case), spread it into an array, and then map the view to the binary representation of each number using Number.toString() with a radix of 2 - .toString(2).
Method 1 - Use the Blob.arrayBuffer() instance method to get a promise that resolves with the ArrayBuffer:
const blobToBinary = async (blob) => {
const buffer = await blob.arrayBuffer();
const view = new Int8Array(buffer);
return [...view].map((n) => n.toString(2)).join(' ');
};
const blob = new Blob(["Example"], { type: "text/plain" });
blobToBinary(blob).then(console.log);
Method 2 - Extract the data from the blob using a FileReader. To get an ArrayBuffer use FileReader.readAsArrayBuffer().
const blob = new Blob(["Example"], { type: "text/plain" });
const reader = new FileReader();
reader.addEventListener("loadend", function() {
const view = new Int8Array(reader.result);
const bin = [...view].map((n) => n.toString(2)).join(' ');
console.log(bin);
});
reader.readAsArrayBuffer(blob);

You can use a FileReader to get the contents of the BLOB as a byte array:
var reader = new FileReader();
reader.readAsArrayBuffer(blob);
reader.onloadend = (event) => {
// The contents of the BLOB are in reader.result:
console.log(reader.result);
}
https://developer.mozilla.org/en-US/docs/Web/API/FileReader
https://developer.mozilla.org/en-US/docs/Web/API/Blob#Example_for_extracting_data_from_a_Blob

How to issue a post to a json rest api with a base64 encoded html input from a SPA [duplicate]

I need to convert my image to a Base64 string so that I can send my image to a server.
Is there any JavaScript file for this? Else, how can I convert it?

There are multiple approaches you can choose from:
1. Approach: FileReader
Load the image as blob via XMLHttpRequest and use the FileReader API (readAsDataURL()) to convert it to a dataURL:
function toDataURL(url, callback) {
var xhr = new XMLHttpRequest();
xhr.onload = function() {
var reader = new FileReader();
reader.onloadend = function() {
callback(reader.result);
}
reader.readAsDataURL(xhr.response);
};
xhr.open('GET', url);
xhr.responseType = 'blob';
xhr.send();
}
toDataURL('https://www.gravatar.com/avatar/d50c83cc0c6523b4d3f6085295c953e0', function(dataUrl) {
console.log('RESULT:', dataUrl)
})
This code example could also be implemented using the WHATWG fetch API:
const toDataURL = url => fetch(url)
.then(response => response.blob())
.then(blob => new Promise((resolve, reject) => {
const reader = new FileReader()
reader.onloadend = () => resolve(reader.result)
reader.onerror = reject
reader.readAsDataURL(blob)
}))
toDataURL('https://www.gravatar.com/avatar/d50c83cc0c6523b4d3f6085295c953e0')
.then(dataUrl => {
console.log('RESULT:', dataUrl)
})
These approaches:
have better compression
work for other file types as well
Browser Support:
http://caniuse.com/#feat=filereader
http://caniuse.com/#feat=fetch
2. Approach: Canvas (for legacy browsers)
Load the image into an Image-Object, paint it to a nontainted canvas and convert the canvas back to a dataURL.
function toDataURL(src, callback, outputFormat) {
var img = new Image();
img.crossOrigin = 'Anonymous';
img.onload = function() {
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var dataURL;
canvas.height = this.naturalHeight;
canvas.width = this.naturalWidth;
ctx.drawImage(this, 0, 0);
dataURL = canvas.toDataURL(outputFormat);
callback(dataURL);
};
img.src = src;
if (img.complete || img.complete === undefined) {
img.src = "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==";
img.src = src;
}
}
toDataURL(
'https://www.gravatar.com/avatar/d50c83cc0c6523b4d3f6085295c953e0',
function(dataUrl) {
console.log('RESULT:', dataUrl)
}
)
In detail
Supported input formats:
image/png, image/jpeg, image/jpg, image/gif, image/bmp, image/tiff, image/x-icon, image/svg+xml, image/webp, image/xxx
Supported output formats:
image/png, image/jpeg, image/webp(chrome)
Browser Support:
http://caniuse.com/#feat=canvas
Internet Explorer 10 (Internet Explorer 10 just works with same origin images)
3. Approach: Images from the local file system
If you want to convert images from the users file system you need to take a different approach.
Use the FileReader API:
function encodeImageFileAsURL(element) {
var file = element.files[0];
var reader = new FileReader();
reader.onloadend = function() {
console.log('RESULT', reader.result)
}
reader.readAsDataURL(file);
}
<input type="file" onchange="encodeImageFileAsURL(this)" />

You can use the HTML5 <canvas> for it:
Create a canvas, load your image into it and then use toDataURL() to get the Base64 representation (actually, it's a data: URL, but it contains the Base64-encoded image).

This snippet can convert your string, image and even video file to Base64 string data.
<input id="inputFileToLoad" type="file" onchange="encodeImageFileAsURL();" />
<div id="imgTest"></div>
<script type='text/javascript'>
function encodeImageFileAsURL() {
var filesSelected = document.getElementById("inputFileToLoad").files;
if (filesSelected.length > 0) {
var fileToLoad = filesSelected[0];
var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent) {
var srcData = fileLoadedEvent.target.result; // <--- data: base64
var newImage = document.createElement('img');
newImage.src = srcData;
document.getElementById("imgTest").innerHTML = newImage.outerHTML;
alert("Converted Base64 version is " + document.getElementById("imgTest").innerHTML);
console.log("Converted Base64 version is " + document.getElementById("imgTest").innerHTML);
}
fileReader.readAsDataURL(fileToLoad);
}
}
</script>

Basically, if your image is
<img id='Img1' src='someurl'>
then you can convert it like
var c = document.createElement('canvas');
var img = document.getElementById('Img1');
c.height = img.naturalHeight;
c.width = img.naturalWidth;
var ctx = c.getContext('2d');
ctx.drawImage(img, 0, 0, c.width, c.height);
var base64String = c.toDataURL();

Here is what I did:
// Author James Harrington 2014
function base64(file, callback){
var coolFile = {};
function readerOnload(e){
var base64 = btoa(e.target.result);
coolFile.base64 = base64;
callback(coolFile)
};
var reader = new FileReader();
reader.onload = readerOnload;
var file = file[0].files[0];
coolFile.filetype = file.type;
coolFile.size = file.size;
coolFile.filename = file.name;
reader.readAsBinaryString(file);
}
And here is how you use it
base64( $('input[type="file"]'), function(data){
console.log(data.base64)
})

I found that the safest and reliable way to do it is to use FileReader().
Demo: Image to Base64
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="myinput" type="file" onchange="encode();" />
<div id="dummy">
</div>
<div>
<textarea style="width:100%;height:500px;" id="txt">
</textarea>
</div>
<script>
function encode() {
var selectedfile = document.getElementById("myinput").files;
if (selectedfile.length > 0) {
var imageFile = selectedfile[0];
var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent) {
var srcData = fileLoadedEvent.target.result;
var newImage = document.createElement('img');
newImage.src = srcData;
document.getElementById("dummy").innerHTML = newImage.outerHTML;
document.getElementById("txt").value = document.getElementById("dummy").innerHTML;
}
fileReader.readAsDataURL(imageFile);
}
}
</script>
</body>
</html>
UPDATE - THE SAME CODE WITH COMMENTS FOR #AnniekJ REQUEST:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="myinput" type="file" onchange="encode();" />
<div id="dummy">
</div>
<div>
<textarea style="width:100%;height:500px;" id="txt">
</textarea>
</div>
<script>
function encode() {
// Get the file objects that was selected by the user from myinput - a file picker control
var selectedfile = document.getElementById("myinput").files;
// Check that the user actually selected file/s from the "file picker" control
// Note - selectedfile is an array, hence we check it`s length, when length of the array
// is bigger than 0 than it means the array containes file objects
if (selectedfile.length > 0) {
// Set the first file object inside the array to this variable
// Note: if multiple files are selected we can itterate on all of the selectedfile array using a for loop - BUT in order to not make this example complicated we only take the first file object that was selected
var imageFile = selectedfile[0];
// Set a filereader object to asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read.
var fileReader = new FileReader();
// We declare an event of the fileReader class (onload event) and we register an anonimous function that will be executed when the event is raised. it is "trick" we preapare in order for the onload event to be raised after the last line of this code will be executed (fileReader.readAsDataURL(imageFile);) - please read about events in javascript if you are not familiar with "Events"
fileReader.onload = function(fileLoadedEvent) {
// AT THIS STAGE THE EVENT WAS RAISED
// Here we are getting the file contents - basiccaly the base64 mapping
var srcData = fileLoadedEvent.target.result;
// We create an image html element dinamically in order to display the image
var newImage = document.createElement('img');
// We set the source of the image we created
newImage.src = srcData;
// ANOTHER TRICK TO EXTRACT THE BASE64 STRING
// We set the outer html of the new image to the div element
document.getElementById("dummy").innerHTML = newImage.outerHTML;
// Then we take the inner html of the div and we have the base64 string
document.getElementById("txt").value = document.getElementById("dummy").innerHTML;
}
// This line will raise the fileReader.onload event - note we are passing the file object here as an argument to the function of the event
fileReader.readAsDataURL(imageFile);
}
}
</script>
</body>
</html>

If you have a file object, this simple function will work:
function getBase64 (file, callback) {
const reader = new FileReader();
reader.addEventListener('load', () => callback(reader.result));
reader.readAsDataURL(file);
}
Usage example:
getBase64(fileObjectFromInput, function(base64Data){
console.log("Base64 of file is", base64Data); // Here you can have your code which uses Base64 for its operation, // file to Base64 by oneshubh
});

I ended up using a function that returns a Promise.
const getImg64 = async() => {
const convertImgToBase64URL = (url) => {
console.log(url)
return new Promise((resolve, reject) => {
const img = new Image();
img.crossOrigin = 'Anonymous';
img.onload = () => {
let canvas = document.createElement('CANVAS')
const ctx = canvas.getContext('2d')
canvas.height = img.height;
canvas.width = img.width;
ctx.drawImage(img, 0, 0);
const dataURL = canvas.toDataURL();
canvas = null;
resolve(dataURL)
}
img.src = url;
})
}
//for the demonstration purposes I used proxy server to avoid cross origin error
const proxyUrl = 'https://cors-anywhere.herokuapp.com/'
const image = await convertImgToBase64URL(proxyUrl+'https://image.shutterstock.com/image-vector/vector-line-icon-hello-wave-260nw-1521867944.jpg')
console.log(image)
}
getImg64()
You can use this approach in any async function. Then you can just await for the converted image and continue with instructions.

uploadProfile(e) {
let file = e.target.files[0];
let reader = new FileReader();
reader.onloadend = function() {
console.log('RESULT', reader.result)
}
reader.readAsDataURL(file);
}

Here is the way you can do with Javascript Promise.
const getBase64 = (file) => new Promise(function (resolve, reject) {
let reader = new FileReader();
reader.readAsDataURL(file);
reader.onload = () => resolve(reader.result)
reader.onerror = (error) => reject('Error: ', error);
})
Now, use it in event handler.
const _changeImg = (e) => {
const file = e.target.files[0];
let encoded;
getBase64(file)
.then((result) => {
encoded = result;
})
.catch(e => console.log(e))
}

You could use FileAPI, but it's pretty much unsupported.

As far as I know, an image can be converted into a Base64 string either by FileReader() or storing it in the canvas element and then use toDataURL() to get the image. I had the similar kind of problem you can refer this.
Convert an image to canvas that is already loaded

Try this code:
For a file upload change event, call this function:
$("#fileproof").on('change', function () {
readImage($(this)).done(function (base64Data) { $('#<%=hfimgbs64.ClientID%>').val(base64Data); });
});
function readImage(inputElement) {
var deferred = $.Deferred();
var files = inputElement.get(0).files;
if (files && files[0]) {
var fr = new FileReader();
fr.onload = function (e) {
deferred.resolve(e.target.result);
};
fr.readAsDataURL(files[0]);
} else {
deferred.resolve(undefined);
}
return deferred.promise();
}
Store Base64 data in hidden filed to use.

document.querySelector('input').onchange = e => {
const fr = new FileReader()
fr.onloadend = () => document.write(fr.result)
fr.readAsDataURL(e.target.files[0])
}
<input type="file">

Needed to leverage reader to convert blob to base64, prefer to use async-await syntax so I chose to extract reader logic into helper like this:
//* Convert resBlob to base64
export const blobToData = (blob: Blob) => {
return new Promise((resolve) => {
const reader = new FileReader()
reader.onloadend = () => resolve(reader.result)
reader.readAsDataURL(blob)
})
}
and calling it using await in main code:
//* Convert resBlob to dataUrl and resolve
const resData = await blobToData(resBlob)

In the case you are facing cors origin error, there is a simple proxy called cors-fix that loads the image on server and return it as buffer array.
Therefore, we can use fetch to get the image data and filereader to convert it to dataUrl, as described by #HaNdTriX.
function toDataUrl(url) {
fetch(`https://cors-fix.web.app/v1?url=${url}`)
.then(data => data.blob().then(blob => {
const reader = new FileReader();
reader.onloadend = () => {
console.log(reader.result);
};
reader.onerror = () => {
console.log('reader error');
};
reader.readAsDataURL(blob);
}));
}

Well, if you are using Dojo Toolkit, it gives us a direct way to encode or decode into Base64.
Try this:
To encode an array of bytes using dojox.encoding.base64:
var str = dojox.encoding.base64.encode(myByteArray);
To decode a Base64-encoded string:
var bytes = dojox.encoding.base64.decode(str);

You can also simply extract base-64 only part of the URL by ding this:
var Base64URL = canvas.toDataURL('image/webp')
var Base64 = Base64URL.split(",")[1] //Returns the base64 part

Assuming that you are doing this in a browser:
With await:
import axios from 'axios'
const response = await axios.get(url, { responseType: 'blob' });
return window.URL.createObjectURL(response.data);
With promise
import axios from 'axios'
const response = await axios.get(url, { responseType: 'blob' })
.then((response) => {
const dataUrl = window.URL.createObjectURL(response.data);
// do something with your url
});

This is very simple.
1> Just call the function and pass your image.
2> Save the return value and use wherever required.
//call like this
const convertedFile = await imageToBase64(fileObj);
console.log("convertedFile",convertedFile);
//this is the required function
async function imageToBase64(image) {
const reader = new FileReader();
reader.readAsDataURL(image);
const data= await new Promise((resolve, reject) => {
reader.onload = () => resolve(reader.result);
reader.onerror = error => reject(error);
});
return data;
}
export default imageToBase64;

Angular 2 - Image to base64 [duplicate]

I need to convert my image to a Base64 string so that I can send my image to a server.
Is there any JavaScript file for this? Else, how can I convert it?

There are multiple approaches you can choose from:
1. Approach: FileReader
Load the image as blob via XMLHttpRequest and use the FileReader API (readAsDataURL()) to convert it to a dataURL:
function toDataURL(url, callback) {
var xhr = new XMLHttpRequest();
xhr.onload = function() {
var reader = new FileReader();
reader.onloadend = function() {
callback(reader.result);
}
reader.readAsDataURL(xhr.response);
};
xhr.open('GET', url);
xhr.responseType = 'blob';
xhr.send();
}
toDataURL('https://www.gravatar.com/avatar/d50c83cc0c6523b4d3f6085295c953e0', function(dataUrl) {
console.log('RESULT:', dataUrl)
})
This code example could also be implemented using the WHATWG fetch API:
const toDataURL = url => fetch(url)
.then(response => response.blob())
.then(blob => new Promise((resolve, reject) => {
const reader = new FileReader()
reader.onloadend = () => resolve(reader.result)
reader.onerror = reject
reader.readAsDataURL(blob)
}))
toDataURL('https://www.gravatar.com/avatar/d50c83cc0c6523b4d3f6085295c953e0')
.then(dataUrl => {
console.log('RESULT:', dataUrl)
})
These approaches:
have better compression
work for other file types as well
Browser Support:
http://caniuse.com/#feat=filereader
http://caniuse.com/#feat=fetch
2. Approach: Canvas (for legacy browsers)
Load the image into an Image-Object, paint it to a nontainted canvas and convert the canvas back to a dataURL.
function toDataURL(src, callback, outputFormat) {
var img = new Image();
img.crossOrigin = 'Anonymous';
img.onload = function() {
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var dataURL;
canvas.height = this.naturalHeight;
canvas.width = this.naturalWidth;
ctx.drawImage(this, 0, 0);
dataURL = canvas.toDataURL(outputFormat);
callback(dataURL);
};
img.src = src;
if (img.complete || img.complete === undefined) {
img.src = "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==";
img.src = src;
}
}
toDataURL(
'https://www.gravatar.com/avatar/d50c83cc0c6523b4d3f6085295c953e0',
function(dataUrl) {
console.log('RESULT:', dataUrl)
}
)
In detail
Supported input formats:
image/png, image/jpeg, image/jpg, image/gif, image/bmp, image/tiff, image/x-icon, image/svg+xml, image/webp, image/xxx
Supported output formats:
image/png, image/jpeg, image/webp(chrome)
Browser Support:
http://caniuse.com/#feat=canvas
Internet Explorer 10 (Internet Explorer 10 just works with same origin images)
3. Approach: Images from the local file system
If you want to convert images from the users file system you need to take a different approach.
Use the FileReader API:
function encodeImageFileAsURL(element) {
var file = element.files[0];
var reader = new FileReader();
reader.onloadend = function() {
console.log('RESULT', reader.result)
}
reader.readAsDataURL(file);
}
<input type="file" onchange="encodeImageFileAsURL(this)" />

You can use the HTML5 <canvas> for it:
Create a canvas, load your image into it and then use toDataURL() to get the Base64 representation (actually, it's a data: URL, but it contains the Base64-encoded image).

This snippet can convert your string, image and even video file to Base64 string data.
<input id="inputFileToLoad" type="file" onchange="encodeImageFileAsURL();" />
<div id="imgTest"></div>
<script type='text/javascript'>
function encodeImageFileAsURL() {
var filesSelected = document.getElementById("inputFileToLoad").files;
if (filesSelected.length > 0) {
var fileToLoad = filesSelected[0];
var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent) {
var srcData = fileLoadedEvent.target.result; // <--- data: base64
var newImage = document.createElement('img');
newImage.src = srcData;
document.getElementById("imgTest").innerHTML = newImage.outerHTML;
alert("Converted Base64 version is " + document.getElementById("imgTest").innerHTML);
console.log("Converted Base64 version is " + document.getElementById("imgTest").innerHTML);
}
fileReader.readAsDataURL(fileToLoad);
}
}
</script>

Basically, if your image is
<img id='Img1' src='someurl'>
then you can convert it like
var c = document.createElement('canvas');
var img = document.getElementById('Img1');
c.height = img.naturalHeight;
c.width = img.naturalWidth;
var ctx = c.getContext('2d');
ctx.drawImage(img, 0, 0, c.width, c.height);
var base64String = c.toDataURL();

Here is what I did:
// Author James Harrington 2014
function base64(file, callback){
var coolFile = {};
function readerOnload(e){
var base64 = btoa(e.target.result);
coolFile.base64 = base64;
callback(coolFile)
};
var reader = new FileReader();
reader.onload = readerOnload;
var file = file[0].files[0];
coolFile.filetype = file.type;
coolFile.size = file.size;
coolFile.filename = file.name;
reader.readAsBinaryString(file);
}
And here is how you use it
base64( $('input[type="file"]'), function(data){
console.log(data.base64)
})

I found that the safest and reliable way to do it is to use FileReader().
Demo: Image to Base64
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="myinput" type="file" onchange="encode();" />
<div id="dummy">
</div>
<div>
<textarea style="width:100%;height:500px;" id="txt">
</textarea>
</div>
<script>
function encode() {
var selectedfile = document.getElementById("myinput").files;
if (selectedfile.length > 0) {
var imageFile = selectedfile[0];
var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent) {
var srcData = fileLoadedEvent.target.result;
var newImage = document.createElement('img');
newImage.src = srcData;
document.getElementById("dummy").innerHTML = newImage.outerHTML;
document.getElementById("txt").value = document.getElementById("dummy").innerHTML;
}
fileReader.readAsDataURL(imageFile);
}
}
</script>
</body>
</html>
UPDATE - THE SAME CODE WITH COMMENTS FOR #AnniekJ REQUEST:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="myinput" type="file" onchange="encode();" />
<div id="dummy">
</div>
<div>
<textarea style="width:100%;height:500px;" id="txt">
</textarea>
</div>
<script>
function encode() {
// Get the file objects that was selected by the user from myinput - a file picker control
var selectedfile = document.getElementById("myinput").files;
// Check that the user actually selected file/s from the "file picker" control
// Note - selectedfile is an array, hence we check it`s length, when length of the array
// is bigger than 0 than it means the array containes file objects
if (selectedfile.length > 0) {
// Set the first file object inside the array to this variable
// Note: if multiple files are selected we can itterate on all of the selectedfile array using a for loop - BUT in order to not make this example complicated we only take the first file object that was selected
var imageFile = selectedfile[0];
// Set a filereader object to asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read.
var fileReader = new FileReader();
// We declare an event of the fileReader class (onload event) and we register an anonimous function that will be executed when the event is raised. it is "trick" we preapare in order for the onload event to be raised after the last line of this code will be executed (fileReader.readAsDataURL(imageFile);) - please read about events in javascript if you are not familiar with "Events"
fileReader.onload = function(fileLoadedEvent) {
// AT THIS STAGE THE EVENT WAS RAISED
// Here we are getting the file contents - basiccaly the base64 mapping
var srcData = fileLoadedEvent.target.result;
// We create an image html element dinamically in order to display the image
var newImage = document.createElement('img');
// We set the source of the image we created
newImage.src = srcData;
// ANOTHER TRICK TO EXTRACT THE BASE64 STRING
// We set the outer html of the new image to the div element
document.getElementById("dummy").innerHTML = newImage.outerHTML;
// Then we take the inner html of the div and we have the base64 string
document.getElementById("txt").value = document.getElementById("dummy").innerHTML;
}
// This line will raise the fileReader.onload event - note we are passing the file object here as an argument to the function of the event
fileReader.readAsDataURL(imageFile);
}
}
</script>
</body>
</html>

If you have a file object, this simple function will work:
function getBase64 (file, callback) {
const reader = new FileReader();
reader.addEventListener('load', () => callback(reader.result));
reader.readAsDataURL(file);
}
Usage example:
getBase64(fileObjectFromInput, function(base64Data){
console.log("Base64 of file is", base64Data); // Here you can have your code which uses Base64 for its operation, // file to Base64 by oneshubh
});

I ended up using a function that returns a Promise.
const getImg64 = async() => {
const convertImgToBase64URL = (url) => {
console.log(url)
return new Promise((resolve, reject) => {
const img = new Image();
img.crossOrigin = 'Anonymous';
img.onload = () => {
let canvas = document.createElement('CANVAS')
const ctx = canvas.getContext('2d')
canvas.height = img.height;
canvas.width = img.width;
ctx.drawImage(img, 0, 0);
const dataURL = canvas.toDataURL();
canvas = null;
resolve(dataURL)
}
img.src = url;
})
}
//for the demonstration purposes I used proxy server to avoid cross origin error
const proxyUrl = 'https://cors-anywhere.herokuapp.com/'
const image = await convertImgToBase64URL(proxyUrl+'https://image.shutterstock.com/image-vector/vector-line-icon-hello-wave-260nw-1521867944.jpg')
console.log(image)
}
getImg64()
You can use this approach in any async function. Then you can just await for the converted image and continue with instructions.

uploadProfile(e) {
let file = e.target.files[0];
let reader = new FileReader();
reader.onloadend = function() {
console.log('RESULT', reader.result)
}
reader.readAsDataURL(file);
}

Here is the way you can do with Javascript Promise.
const getBase64 = (file) => new Promise(function (resolve, reject) {
let reader = new FileReader();
reader.readAsDataURL(file);
reader.onload = () => resolve(reader.result)
reader.onerror = (error) => reject('Error: ', error);
})
Now, use it in event handler.
const _changeImg = (e) => {
const file = e.target.files[0];
let encoded;
getBase64(file)
.then((result) => {
encoded = result;
})
.catch(e => console.log(e))
}

You could use FileAPI, but it's pretty much unsupported.

As far as I know, an image can be converted into a Base64 string either by FileReader() or storing it in the canvas element and then use toDataURL() to get the image. I had the similar kind of problem you can refer this.
Convert an image to canvas that is already loaded

Try this code:
For a file upload change event, call this function:
$("#fileproof").on('change', function () {
readImage($(this)).done(function (base64Data) { $('#<%=hfimgbs64.ClientID%>').val(base64Data); });
});
function readImage(inputElement) {
var deferred = $.Deferred();
var files = inputElement.get(0).files;
if (files && files[0]) {
var fr = new FileReader();
fr.onload = function (e) {
deferred.resolve(e.target.result);
};
fr.readAsDataURL(files[0]);
} else {
deferred.resolve(undefined);
}
return deferred.promise();
}
Store Base64 data in hidden filed to use.

document.querySelector('input').onchange = e => {
const fr = new FileReader()
fr.onloadend = () => document.write(fr.result)
fr.readAsDataURL(e.target.files[0])
}
<input type="file">

Needed to leverage reader to convert blob to base64, prefer to use async-await syntax so I chose to extract reader logic into helper like this:
//* Convert resBlob to base64
export const blobToData = (blob: Blob) => {
return new Promise((resolve) => {
const reader = new FileReader()
reader.onloadend = () => resolve(reader.result)
reader.readAsDataURL(blob)
})
}
and calling it using await in main code:
//* Convert resBlob to dataUrl and resolve
const resData = await blobToData(resBlob)

In the case you are facing cors origin error, there is a simple proxy called cors-fix that loads the image on server and return it as buffer array.
Therefore, we can use fetch to get the image data and filereader to convert it to dataUrl, as described by #HaNdTriX.
function toDataUrl(url) {
fetch(`https://cors-fix.web.app/v1?url=${url}`)
.then(data => data.blob().then(blob => {
const reader = new FileReader();
reader.onloadend = () => {
console.log(reader.result);
};
reader.onerror = () => {
console.log('reader error');
};
reader.readAsDataURL(blob);
}));
}

Well, if you are using Dojo Toolkit, it gives us a direct way to encode or decode into Base64.
Try this:
To encode an array of bytes using dojox.encoding.base64:
var str = dojox.encoding.base64.encode(myByteArray);
To decode a Base64-encoded string:
var bytes = dojox.encoding.base64.decode(str);

You can also simply extract base-64 only part of the URL by ding this:
var Base64URL = canvas.toDataURL('image/webp')
var Base64 = Base64URL.split(",")[1] //Returns the base64 part

Assuming that you are doing this in a browser:
With await:
import axios from 'axios'
const response = await axios.get(url, { responseType: 'blob' });
return window.URL.createObjectURL(response.data);
With promise
import axios from 'axios'
const response = await axios.get(url, { responseType: 'blob' })
.then((response) => {
const dataUrl = window.URL.createObjectURL(response.data);
// do something with your url
});

This is very simple.
1> Just call the function and pass your image.
2> Save the return value and use wherever required.
//call like this
const convertedFile = await imageToBase64(fileObj);
console.log("convertedFile",convertedFile);
//this is the required function
async function imageToBase64(image) {
const reader = new FileReader();
reader.readAsDataURL(image);
const data= await new Promise((resolve, reject) => {
reader.onload = () => resolve(reader.result);
reader.onerror = error => reject(error);
});
return data;
}
export default imageToBase64;

JavaScript/jQuery - Convert Image to Base64 [duplicate]

I need to convert my image to a Base64 string so that I can send my image to a server.
Is there any JavaScript file for this? Else, how can I convert it?

There are multiple approaches you can choose from:
1. Approach: FileReader
Load the image as blob via XMLHttpRequest and use the FileReader API (readAsDataURL()) to convert it to a dataURL:
function toDataURL(url, callback) {
var xhr = new XMLHttpRequest();
xhr.onload = function() {
var reader = new FileReader();
reader.onloadend = function() {
callback(reader.result);
}
reader.readAsDataURL(xhr.response);
};
xhr.open('GET', url);
xhr.responseType = 'blob';
xhr.send();
}
toDataURL('https://www.gravatar.com/avatar/d50c83cc0c6523b4d3f6085295c953e0', function(dataUrl) {
console.log('RESULT:', dataUrl)
})
This code example could also be implemented using the WHATWG fetch API:
const toDataURL = url => fetch(url)
.then(response => response.blob())
.then(blob => new Promise((resolve, reject) => {
const reader = new FileReader()
reader.onloadend = () => resolve(reader.result)
reader.onerror = reject
reader.readAsDataURL(blob)
}))
toDataURL('https://www.gravatar.com/avatar/d50c83cc0c6523b4d3f6085295c953e0')
.then(dataUrl => {
console.log('RESULT:', dataUrl)
})
These approaches:
have better compression
work for other file types as well
Browser Support:
http://caniuse.com/#feat=filereader
http://caniuse.com/#feat=fetch
2. Approach: Canvas (for legacy browsers)
Load the image into an Image-Object, paint it to a nontainted canvas and convert the canvas back to a dataURL.
function toDataURL(src, callback, outputFormat) {
var img = new Image();
img.crossOrigin = 'Anonymous';
img.onload = function() {
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var dataURL;
canvas.height = this.naturalHeight;
canvas.width = this.naturalWidth;
ctx.drawImage(this, 0, 0);
dataURL = canvas.toDataURL(outputFormat);
callback(dataURL);
};
img.src = src;
if (img.complete || img.complete === undefined) {
img.src = "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==";
img.src = src;
}
}
toDataURL(
'https://www.gravatar.com/avatar/d50c83cc0c6523b4d3f6085295c953e0',
function(dataUrl) {
console.log('RESULT:', dataUrl)
}
)
In detail
Supported input formats:
image/png, image/jpeg, image/jpg, image/gif, image/bmp, image/tiff, image/x-icon, image/svg+xml, image/webp, image/xxx
Supported output formats:
image/png, image/jpeg, image/webp(chrome)
Browser Support:
http://caniuse.com/#feat=canvas
Internet Explorer 10 (Internet Explorer 10 just works with same origin images)
3. Approach: Images from the local file system
If you want to convert images from the users file system you need to take a different approach.
Use the FileReader API:
function encodeImageFileAsURL(element) {
var file = element.files[0];
var reader = new FileReader();
reader.onloadend = function() {
console.log('RESULT', reader.result)
}
reader.readAsDataURL(file);
}
<input type="file" onchange="encodeImageFileAsURL(this)" />

You can use the HTML5 <canvas> for it:
Create a canvas, load your image into it and then use toDataURL() to get the Base64 representation (actually, it's a data: URL, but it contains the Base64-encoded image).

This snippet can convert your string, image and even video file to Base64 string data.
<input id="inputFileToLoad" type="file" onchange="encodeImageFileAsURL();" />
<div id="imgTest"></div>
<script type='text/javascript'>
function encodeImageFileAsURL() {
var filesSelected = document.getElementById("inputFileToLoad").files;
if (filesSelected.length > 0) {
var fileToLoad = filesSelected[0];
var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent) {
var srcData = fileLoadedEvent.target.result; // <--- data: base64
var newImage = document.createElement('img');
newImage.src = srcData;
document.getElementById("imgTest").innerHTML = newImage.outerHTML;
alert("Converted Base64 version is " + document.getElementById("imgTest").innerHTML);
console.log("Converted Base64 version is " + document.getElementById("imgTest").innerHTML);
}
fileReader.readAsDataURL(fileToLoad);
}
}
</script>

Basically, if your image is
<img id='Img1' src='someurl'>
then you can convert it like
var c = document.createElement('canvas');
var img = document.getElementById('Img1');
c.height = img.naturalHeight;
c.width = img.naturalWidth;
var ctx = c.getContext('2d');
ctx.drawImage(img, 0, 0, c.width, c.height);
var base64String = c.toDataURL();

Here is what I did:
// Author James Harrington 2014
function base64(file, callback){
var coolFile = {};
function readerOnload(e){
var base64 = btoa(e.target.result);
coolFile.base64 = base64;
callback(coolFile)
};
var reader = new FileReader();
reader.onload = readerOnload;
var file = file[0].files[0];
coolFile.filetype = file.type;
coolFile.size = file.size;
coolFile.filename = file.name;
reader.readAsBinaryString(file);
}
And here is how you use it
base64( $('input[type="file"]'), function(data){
console.log(data.base64)
})

I found that the safest and reliable way to do it is to use FileReader().
Demo: Image to Base64
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="myinput" type="file" onchange="encode();" />
<div id="dummy">
</div>
<div>
<textarea style="width:100%;height:500px;" id="txt">
</textarea>
</div>
<script>
function encode() {
var selectedfile = document.getElementById("myinput").files;
if (selectedfile.length > 0) {
var imageFile = selectedfile[0];
var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent) {
var srcData = fileLoadedEvent.target.result;
var newImage = document.createElement('img');
newImage.src = srcData;
document.getElementById("dummy").innerHTML = newImage.outerHTML;
document.getElementById("txt").value = document.getElementById("dummy").innerHTML;
}
fileReader.readAsDataURL(imageFile);
}
}
</script>
</body>
</html>
UPDATE - THE SAME CODE WITH COMMENTS FOR #AnniekJ REQUEST:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="myinput" type="file" onchange="encode();" />
<div id="dummy">
</div>
<div>
<textarea style="width:100%;height:500px;" id="txt">
</textarea>
</div>
<script>
function encode() {
// Get the file objects that was selected by the user from myinput - a file picker control
var selectedfile = document.getElementById("myinput").files;
// Check that the user actually selected file/s from the "file picker" control
// Note - selectedfile is an array, hence we check it`s length, when length of the array
// is bigger than 0 than it means the array containes file objects
if (selectedfile.length > 0) {
// Set the first file object inside the array to this variable
// Note: if multiple files are selected we can itterate on all of the selectedfile array using a for loop - BUT in order to not make this example complicated we only take the first file object that was selected
var imageFile = selectedfile[0];
// Set a filereader object to asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read.
var fileReader = new FileReader();
// We declare an event of the fileReader class (onload event) and we register an anonimous function that will be executed when the event is raised. it is "trick" we preapare in order for the onload event to be raised after the last line of this code will be executed (fileReader.readAsDataURL(imageFile);) - please read about events in javascript if you are not familiar with "Events"
fileReader.onload = function(fileLoadedEvent) {
// AT THIS STAGE THE EVENT WAS RAISED
// Here we are getting the file contents - basiccaly the base64 mapping
var srcData = fileLoadedEvent.target.result;
// We create an image html element dinamically in order to display the image
var newImage = document.createElement('img');
// We set the source of the image we created
newImage.src = srcData;
// ANOTHER TRICK TO EXTRACT THE BASE64 STRING
// We set the outer html of the new image to the div element
document.getElementById("dummy").innerHTML = newImage.outerHTML;
// Then we take the inner html of the div and we have the base64 string
document.getElementById("txt").value = document.getElementById("dummy").innerHTML;
}
// This line will raise the fileReader.onload event - note we are passing the file object here as an argument to the function of the event
fileReader.readAsDataURL(imageFile);
}
}
</script>
</body>
</html>

If you have a file object, this simple function will work:
function getBase64 (file, callback) {
const reader = new FileReader();
reader.addEventListener('load', () => callback(reader.result));
reader.readAsDataURL(file);
}
Usage example:
getBase64(fileObjectFromInput, function(base64Data){
console.log("Base64 of file is", base64Data); // Here you can have your code which uses Base64 for its operation, // file to Base64 by oneshubh
});

I ended up using a function that returns a Promise.
const getImg64 = async() => {
const convertImgToBase64URL = (url) => {
console.log(url)
return new Promise((resolve, reject) => {
const img = new Image();
img.crossOrigin = 'Anonymous';
img.onload = () => {
let canvas = document.createElement('CANVAS')
const ctx = canvas.getContext('2d')
canvas.height = img.height;
canvas.width = img.width;
ctx.drawImage(img, 0, 0);
const dataURL = canvas.toDataURL();
canvas = null;
resolve(dataURL)
}
img.src = url;
})
}
//for the demonstration purposes I used proxy server to avoid cross origin error
const proxyUrl = 'https://cors-anywhere.herokuapp.com/'
const image = await convertImgToBase64URL(proxyUrl+'https://image.shutterstock.com/image-vector/vector-line-icon-hello-wave-260nw-1521867944.jpg')
console.log(image)
}
getImg64()
You can use this approach in any async function. Then you can just await for the converted image and continue with instructions.

uploadProfile(e) {
let file = e.target.files[0];
let reader = new FileReader();
reader.onloadend = function() {
console.log('RESULT', reader.result)
}
reader.readAsDataURL(file);
}

Here is the way you can do with Javascript Promise.
const getBase64 = (file) => new Promise(function (resolve, reject) {
let reader = new FileReader();
reader.readAsDataURL(file);
reader.onload = () => resolve(reader.result)
reader.onerror = (error) => reject('Error: ', error);
})
Now, use it in event handler.
const _changeImg = (e) => {
const file = e.target.files[0];
let encoded;
getBase64(file)
.then((result) => {
encoded = result;
})
.catch(e => console.log(e))
}

You could use FileAPI, but it's pretty much unsupported.

As far as I know, an image can be converted into a Base64 string either by FileReader() or storing it in the canvas element and then use toDataURL() to get the image. I had the similar kind of problem you can refer this.
Convert an image to canvas that is already loaded

Try this code:
For a file upload change event, call this function:
$("#fileproof").on('change', function () {
readImage($(this)).done(function (base64Data) { $('#<%=hfimgbs64.ClientID%>').val(base64Data); });
});
function readImage(inputElement) {
var deferred = $.Deferred();
var files = inputElement.get(0).files;
if (files && files[0]) {
var fr = new FileReader();
fr.onload = function (e) {
deferred.resolve(e.target.result);
};
fr.readAsDataURL(files[0]);
} else {
deferred.resolve(undefined);
}
return deferred.promise();
}
Store Base64 data in hidden filed to use.

document.querySelector('input').onchange = e => {
const fr = new FileReader()
fr.onloadend = () => document.write(fr.result)
fr.readAsDataURL(e.target.files[0])
}
<input type="file">

Needed to leverage reader to convert blob to base64, prefer to use async-await syntax so I chose to extract reader logic into helper like this:
//* Convert resBlob to base64
export const blobToData = (blob: Blob) => {
return new Promise((resolve) => {
const reader = new FileReader()
reader.onloadend = () => resolve(reader.result)
reader.readAsDataURL(blob)
})
}
and calling it using await in main code:
//* Convert resBlob to dataUrl and resolve
const resData = await blobToData(resBlob)

In the case you are facing cors origin error, there is a simple proxy called cors-fix that loads the image on server and return it as buffer array.
Therefore, we can use fetch to get the image data and filereader to convert it to dataUrl, as described by #HaNdTriX.
function toDataUrl(url) {
fetch(`https://cors-fix.web.app/v1?url=${url}`)
.then(data => data.blob().then(blob => {
const reader = new FileReader();
reader.onloadend = () => {
console.log(reader.result);
};
reader.onerror = () => {
console.log('reader error');
};
reader.readAsDataURL(blob);
}));
}

Well, if you are using Dojo Toolkit, it gives us a direct way to encode or decode into Base64.
Try this:
To encode an array of bytes using dojox.encoding.base64:
var str = dojox.encoding.base64.encode(myByteArray);
To decode a Base64-encoded string:
var bytes = dojox.encoding.base64.decode(str);

You can also simply extract base-64 only part of the URL by ding this:
var Base64URL = canvas.toDataURL('image/webp')
var Base64 = Base64URL.split(",")[1] //Returns the base64 part

Assuming that you are doing this in a browser:
With await:
import axios from 'axios'
const response = await axios.get(url, { responseType: 'blob' });
return window.URL.createObjectURL(response.data);
With promise
import axios from 'axios'
const response = await axios.get(url, { responseType: 'blob' })
.then((response) => {
const dataUrl = window.URL.createObjectURL(response.data);
// do something with your url
});

This is very simple.
1> Just call the function and pass your image.
2> Save the return value and use wherever required.
//call like this
const convertedFile = await imageToBase64(fileObj);
console.log("convertedFile",convertedFile);
//this is the required function
async function imageToBase64(image) {
const reader = new FileReader();
reader.readAsDataURL(image);
const data= await new Promise((resolve, reject) => {
reader.onload = () => resolve(reader.result);
reader.onerror = error => reject(error);
});
return data;
}
export default imageToBase64;

How can I console.log() a Blob object?

I have a Blob object I want to inspect by logging its value. All I can see are type and size properties. Is there a way to do this?

Basic example on using a FileReader to look at the content in a blob
var html= ['<a id="anchor">Hello World</a>'];
var myBlob = new Blob(html, { type: 'text/xml'});
var myReader = new FileReader();
myReader.onload = function(event){
console.log(JSON.stringify(myReader.result));
};
myReader.readAsText(myBlob);

First of all we should create a function for converting blob to base64:
const blobToBase64 = blob => {
const reader = new FileReader();
reader.readAsDataURL(blob);
return new Promise(resolve => {
reader.onloadend = () => {
resolve(reader.result);
};
});
};
Then we can use this function to use it for console.log:
blobToBase64(blobData).then(res => {
console.log(res); // res is base64 now
// even you can click on it to see it in a new tab
});

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