Image convert to Base64

小开

最佳答案

function readFile() {
  

if (!this.files || !this.files[0]) return;
    

const FR = new FileReader();
    

FR.addEventListener("load", function(evt) {
document.querySelector("#img").src         = evt.target.result;
document.querySelector("#b64").textContent = evt.target.result;
});
    

FR.readAsDataURL(this.files[0]);
  

}


document.querySelector("#inp").addEventListener("change", readFile);

<input id="inp" type="file">
<p id="b64"></p>
<img id="img" height="150">

_{(P.S: A base64 encoded image (String) 4/3 the size of the original image data)}

Check this answer for multiple images upload.

Browser support: http://caniuse.com/#search=file%20api
More info here: https://developer.mozilla.org/en-US/docs/Web/API/FileReader

小开

Exactly what you need:) You can choose callback version or Promise version. Note that promises will work in IE only with Promise polyfill lib.You can put this code once on a page, and this function will appear in all your files.

The loadend event is fired when progress has stopped on the loading of a resource (e.g. after "error", "abort", or "load" have been dispatched)

Callback version

        File.prototype.convertToBase64 = function(callback){
var reader = new FileReader();
reader.onloadend = function (e) {
callback(e.target.result, e.target.error);
};
reader.readAsDataURL(this);
};


$("#asd").on('change',function(){
var selectedFile = this.files[0];
selectedFile.convertToBase64(function(base64){
alert(base64);
})
});

Promise version

    File.prototype.convertToBase64 = function(){
return new Promise(function(resolve, reject) {
var reader = new FileReader();
reader.onloadend = function (e) {
resolve({
fileName: this.name,
result: e.target.result,
error: e.target.error
});
};
reader.readAsDataURL(this);
}.bind(this));
};


FileList.prototype.convertAllToBase64 = function(regexp){
// empty regexp if not set
regexp = regexp || /.*/;
//making array from FileList
var filesArray = Array.prototype.slice.call(this);
var base64PromisesArray = filesArray.
filter(function(file){
return (regexp).test(file.name)
}).map(function(file){
return file.convertToBase64();
});
return Promise.all(base64PromisesArray);
};


$("#asd").on('change',function(){
//for one file
var selectedFile = this.files[0];
selectedFile.convertToBase64().
then(function(obj){
alert(obj.result);
});
});
//for all files that have file extention png, jpeg, jpg, gif
this.files.convertAllToBase64(/\.(png|jpeg|jpg|gif)$/i).then(function(objArray){
objArray.forEach(function(obj, i){
console.log("result[" + obj.fileName + "][" + i + "] = " + obj.result);
});
});
})

html

<input type="file" id="asd" multiple/>

小开

It's useful to work with Deferred Object in this case, and return promise:

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();
}

And above function could be used in this way:

var inputElement = $("input[name=file]");
readImage(inputElement).done(function(base64Data){
alert(base64Data);
});

Or in your case:

$(input).on('change',function(){
readImage($(this)).done(function(base64Data){ alert(base64Data); });
});

小开

<input type="file" onchange="getBaseUrl()">

function getBaseUrl ()  {
var file = document.querySelector('input[type=file]')['files'][0];
var reader = new FileReader();
var baseString;
reader.onloadend = function () {
baseString = reader.result;
console.log(baseString);
};
reader.readAsDataURL(file);
}

小开

// https://developer.mozilla.org/en-US/docs/Web/API/FileReader/readAsDataURL


/* Simple */
function previewImage( image, preview, string )
{


var preview     = document.querySelector( preview );
var fileImage   = image.files[0];


var reader      = new FileReader();


reader.addEventListener( "load", function() {


preview.style.height    = "100";
preview.title           = fileImage.name;


// convert image file to base64 string
preview.src             = reader.result;


/* --- */


document.querySelector( string ).value = reader.result;


}, false );


if ( fileImage )
{
reader.readAsDataURL( fileImage );
}


}


document.querySelector( "#imageID" ).addEventListener( "change", function() {


previewImage( this, "#imagePreviewID", "#imageStringID" );


} )
/* Simple || */

<form>


File Upload: <input type="file" id="imageID" /><br />
Preview: <img src="#" id="imagePreviewID" /><br />
String base64: <textarea id="imageStringID" rows="10" cols="50"></textarea>


</form>

codesanbox

小开

Function convert image to base64 using jquery (you can convert to vanila js). Hope it help to you!

Usage: input is your nameId input has file image

<input type="file" id="asd"/>
<button onclick="proccessData()">Submit</button>


<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>


async function converImageToBase64(inputId) {
let image = $('#'+inputId)[0]['files']


if (image && image[0]) {
const reader = new FileReader();


return new Promise(resolve => {
reader.onload = ev => {
resolve(ev.target.result)
}
reader.readAsDataURL(image[0])
})
}
}


async function proccessData() {
const image = await converImageToBase64('asd')
console.log(image)
}


</script>

Example: converImageToBase64('yourFileInputId')

https://codepen.io/mariohandsome/pen/yLadmVb

小开

For modern Browsers (no IE support)

Html file input

<style>
.upload-button {
background-color: grey;
}


.upload-button input{
display:none;
}
</style>
<label for="upload-photo" class="upload-button">
Upload file
<input
type="file"
id="upload-photo"
</input>
</label>

JS

document.getElementById("upload-photo").addEventListener("change", function({target}){
if (target.files && target.files.length) {
try {
const uploadedImageBase64 = await convertFileToBase64(target.files[0]);
//do something with above data string
} catch() {
//handle error
}
}
})


function convertFileToBase64(file) {
return new Promise((resolve, reject) => {
const reader = new FileReader();
reader.readAsDataURL(file);
reader.onload = () => resolve(reader.result);
reader.onerror = reject;
});
}