Preview images before upload - javascript

I have a page with four images for the user to select. I want the user to be able to preview each image on the site before upload.
The JavaScript code below works for only one image but I would like it to work for multiple images uploaded via <input type="file">.
What will be the best way to do this?
function readURL(input) {
if (input.files && input.files[0]) {
var reader = new FileReader();
reader.onload = function (e) {
$('#output').attr('src', e.target.result);
}
reader.readAsDataURL(input.files[0]);
}
}
$("#file-input").change(function () {
readURL(this);
});

Here is jQuery version for you. I think it more simplest thing.
$(function() {
// Multiple images preview in browser
var imagesPreview = function(input, placeToInsertImagePreview) {
if (input.files) {
var filesAmount = input.files.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
$($.parseHTML('<img>')).attr('src', event.target.result).appendTo(placeToInsertImagePreview);
}
reader.readAsDataURL(input.files[i]);
}
}
};
$('#gallery-photo-add').on('change', function() {
imagesPreview(this, 'div.gallery');
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple id="gallery-photo-add">
<div class="gallery"></div>

Add the multiple attribute to your HTMLInputElement
Add the accept attribute to your HTMLInputElement
To filter your files selection to images only, use accept="image/*", or a comma separated MIME list: accept="image/png, image/jpeg"
Use FileReader.readAsDataURL to get the Base64 string,
or URL.createObjectURL to get the file Blob object
Using FileReader.readAsDataURL
The asynchronous way to read the image data is by using FileReader API and its readAsDataURL method which returns a Base64 String:
const preview = (file) => {
const fr = new FileReader();
fr.onload = () => {
const img = document.createElement("img");
img.src = fr.result; // String Base64
img.alt = file.name;
document.querySelector('#preview').append(img);
};
fr.readAsDataURL(file);
};
document.querySelector("#files").addEventListener("change", (ev) => {
if (!ev.target.files) return; // Do nothing.
[...ev.target.files].forEach(preview);
});
#preview img { max-height: 100px; }
<input id="files" type="file" accept="image/*" multiple>
<div id="preview"></div>
Async strategy:
Due to the asynchronous nature of FileReader, you could implement an async/await strategy:
// DOM utility functions:
const el = (sel, par) => (par || document).querySelector(sel);
const elNew = (tag, props) => Object.assign(document.createElement(tag), props);
// Preview images before upload:
const elFiles = el("#files");
const elPreview = el("#preview");
const previewImage = (props) => elPreview.append(elNew("img", props));
const reader = (file, method = "readAsDataURL") => new Promise((resolve, reject) => {
const fr = new FileReader();
fr.onload = () => resolve({ file, result: fr.result });
fr.onerror = (err) => reject(err);
fr[method](file);
});
const previewImages = async(files) => {
// Remove existing preview images
elPreview.innerHTML = "";
let filesData = [];
try {
// Read all files. Return Array of Promises
const readerPromises = files.map((file) => reader(file));
filesData = await Promise.all(readerPromises);
} catch (err) {
// Notify the user that something went wrong.
elPreview.textContent = "An error occurred while loading images. Try again.";
// In this specific case Promise.all() might be preferred over
// Promise.allSettled(), since it isn't trivial to modify a FileList
// to a subset of files of what the user initially selected.
// Therefore, let's just stash the entire operation.
console.error(err);
return; // Exit function here.
}
// All OK. Preview images:
filesData.forEach(data => {
previewImage({
src: data.result, // Base64 String
alt: data.file.name // File.name String
});
});
};
elFiles.addEventListener("change", (ev) => {
if (!ev.currentTarget.files) return; // Do nothing.
previewImages([...ev.currentTarget.files]);
});
#preview img { max-height: 100px; }
<input id="files" type="file" accept="image/*" multiple>
<div id="preview"></div>
Using URL.createObjectURL
The synchronous way to read the image is by using the URL API and its createObjectURL method which returns a Blob:
const preview = (file) => {
const img = document.createElement("img");
img.src = URL.createObjectURL(file); // Object Blob
img.alt = file.name;
document.querySelector('#preview').append(img);
};
document.querySelector("#files").addEventListener("change", (ev) => {
if (!ev.target.files) return; // Do nothing.
[...ev.target.files].forEach(preview);
});
#preview img { max-height: 120px; }
<input id="files" type="file" accept="image/*" multiple>
<div id="preview"></div>
Although looks much simpler, it has implications on the main thread due to its synchronicity, and requires you to manually use (when possible) URL.revokeObjectURL in order to free up memory:
// Remove unused images from #preview? Consider also using
URL.revokeObjectURL(someImg.src); // Free up memory space
jQuery example:
A jQuery implementation of the above FileReader.readAsDataURL() example:
const preview = (file) => {
const fr = new FileReader();
fr.onload = (ev) => {
$('#preview').append($("<img>", {src: fr.result, alt: file.name}));
};
fr.readAsDataURL(file);
};
$("#files").on("change", (ev) => {
if (!ev.target.files) return; // Do nothing.
[...ev.target.files].forEach(preview);
});
#preview img { max-height: 120px; }
<input id="files" type="file" accept="image/*" multiple>
<div id="preview"></div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.1/jquery.min.js"></script>
Additional read:
File API — Using files from web applications (MDN)
readAsDataURL (MDN)
FileReader result (MDN)
Promise.all() (MDN)
Preview Image, get file size, image height and width before upload
Tips:
Besides using the HTMLInputElement attribute accept, if you want to make sure within JavaScript that a file is-of-type, you could:
if (!/\.(jpe?g|png|gif)$/i.test(file.name)) {
// Not a valid image
}
or like:
if (!/^image\//i.test(file.type)) {
// File is not of type Image
}

function previewMultiple(event){
var saida = document.getElementById("adicionafoto");
var quantos = saida.files.length;
for(i = 0; i < quantos; i++){
var urls = URL.createObjectURL(event.target.files[i]);
document.getElementById("galeria").innerHTML += '<img src="'+urls+'">';
}
}
#galeria{
display: flex;
}
#galeria img{
width: 85px;
height: 85px;
border-radius: 10px;
box-shadow: 0 0 8px rgba(0,0,0,0.2);
opacity: 85%;
}
<input type="file" multiple onchange="previewMultiple(event)" id="adicionafoto">
<div id="galeria">
</div>

Just use FileReader.readAsDataURL()
HTML:
<div id='photos-preview'></div>
<input type="file" id="fileupload" multiple (change)="handleFileInput($event.target.files)" />
JS:
function handleFileInput(fileList: FileList) {
const preview = document.getElementById('photos-preview');
Array.from(fileList).forEach((file: File) => {
const reader = new FileReader();
reader.onload = () => {
var image = new Image();
image.src = String(reader.result);
preview.appendChild(image);
}
reader.readAsDataURL(file);
});
}
DEMO

$(function() {
// Multiple images preview in browser
var imagesPreview = function(input, placeToInsertImagePreview) {
if (input.files) {
var filesAmount = input.files.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
$($.parseHTML('<img>')).attr('src', event.target.result).appendTo(placeToInsertImagePreview);
}
reader.readAsDataURL(input.files[i]);
}
}
};
$('#gallery-photo-add').on('change', function() {
imagesPreview(this, 'div.gallery');
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple id="gallery-photo-add">
<div class="gallery"></div>
function previewImages() {
var preview = document.querySelector('#preview');
if (this.files) {
[].forEach.call(this.files, readAndPreview);
}
function readAndPreview(file) {
// Make sure `file.name` matches our extensions criteria
if (!/\.(jpe?g|png|gif)$/i.test(file.name)) {
return alert(file.name + " is not an image");
} // else...
var reader = new FileReader();
reader.addEventListener("load", function() {
var image = new Image();
image.height = 100;
image.title = file.name;
image.src = this.result;
preview.appendChild(image);
});
reader.readAsDataURL(file);
}
}
document.querySelector('#file-input').addEventListener("change", previewImages);
<input id="file-input" type="file" multiple>
<div id="preview"></div>

function previewImages() {
var preview = document.querySelector('#preview');
if (this.files) {
[].forEach.call(this.files, readAndPreview);
}
function readAndPreview(file) {
// Make sure `file.name` matches our extensions criteria
if (!/\.(jpe?g|png|gif)$/i.test(file.name)) {
return alert(file.name + " is not an image");
} // else...
var reader = new FileReader();
reader.addEventListener("load", function() {
var image = new Image();
image.height = 100;
image.title = file.name;
image.src = this.result;
preview.appendChild(image);
});
reader.readAsDataURL(file);
}
}
document.querySelector('#file-input').addEventListener("change", previewImages);
<input id="file-input" type="file" multiple>
<div id="preview"></div>

<script type="text/javascript">
var upcontrol = {
queue : null, // upload queue
now : 0, // current file being uploaded
start : function (files) {
// upcontrol.start() : start upload queue
// WILL ONLY START IF NO EXISTING UPLOAD QUEUE
if (upcontrol.queue==null) {
// VISUAL - DISABLE UPLOAD UNTIL DONE
upcontrol.queue = files;
document.getElementById('uploader').classList.add('disabled');
// PREVIEW UPLOAD IMAGES
upcontrol.preview();*enter code here*
//PROCESS UPLOAD ON CLICK
$('#add_files').on('click', function() {
upcontrol.run();
});
}
},
preview : function() {
//upcontrol.preview() : preview uploading file
if (upcontrol.queue) {
var filesAmount = upcontrol.queue.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
var fimg = document.createElement('img')
fimg.src = event.target.result,
fimg.classList = "col-sm-6 col-md-6 col-lg-4 float-left center",
document.getElementById('gallery').appendChild(fimg);
}
reader.readAsDataURL(upcontrol.queue[i]);
}
}
},
run : function () {
// upcontrol.run() : proceed upload file
var xhr = new XMLHttpRequest(),
data = new FormData();
data.append('file-upload', upcontrol.queue[upcontrol.now]);
xhr.open('POST', './lockeroom/func/simple-upload.php', true);
xhr.onload = function (e) {
// SHOW UPLOAD STATUS
var fstat = document.createElement('div'),
txt = upcontrol.queue[upcontrol.now].name + " - ";
if (xhr.readyState === 4) {
if (xhr.status === 200) {
// SERVER RESPONSE
txt += xhr.responseText;
} else {
// ERROR
txt += xhr.statusText;
}
}
fstat.innerHTML = txt;
document.getElementById('upstat').appendChild(fstat);
// UPLOAD NEXT FILE
upcontrol.now++;
if (upcontrol.now < upcontrol.queue.length) {
upcontrol.run();
}
// ALL DONE
else {
upcontrol.now = 0;
upcontrol.queue = null;
document.getElementById('uploader').classList.remove('disabled');
}
};
xhr.send(data);
}
};
window.addEventListener("load", function () {
// IF DRAG-DROP UPLOAD SUPPORTED
if (window.File && window.FileReader && window.FileList && window.Blob) {
/* [THE ELEMENTS] */
var uploader = document.getElementById('uploader');
/* [VISUAL - HIGHLIGHT DROP ZONE ON HOVER] */
uploader.addEventListener("dragenter", function (e) {
e.preventDefault();
e.stopPropagation();
uploader.classList.add('highlight');
});
uploader.addEventListener("dragleave", function (e) {
e.preventDefault();
e.stopPropagation();
uploader.classList.remove('highlight');
});
/* [UPLOAD MECHANICS] */
// STOP THE DEFAULT BROWSER ACTION FROM OPENING THE FILE
uploader.addEventListener("dragover", function (e) {
e.preventDefault();
e.stopPropagation();
});
// ADD OUR OWN UPLOAD ACTION
uploader.addEventListener("drop", function (e) {
e.preventDefault();
e.stopPropagation();
uploader.classList.remove('highlight');
upcontrol.start(e.dataTransfer.files);
});
}
// FALLBACK - HIDE DROP ZONE IF DRAG-DROP UPLOAD NOT SUPPORTED
else {
document.getElementById('uploader').style.display = "none";
}
});
</script>
i used somthing like this and i got the best result and easy to understand.

function appendRows(){
$i++;
var html='';
html+='<div id="remove'+$i+'"><input type="file" name="imagefile[]" accept="image/*" onchange="appendloadFile('+$i+')"><img id="outputshow'+$i+'" height="70px" width="90px"><i onclick="deleteRows('+$i+')" class="fas fa-trash-alt"></i></div>';
$("#appendshow").append(html);
}
function appendloadFile(i){
var appendoutput = document.getElementById('outputshow'+i+'');
appendoutput.src = URL.createObjectURL(event.target.files[0]);
}

https://stackoverflow.com/a/59985954/8784402
ES2017 Way
// convert file to a base64 url
const readURL = file => {
return new Promise((res, rej) => {
const reader = new FileReader();
reader.onload = e => res(e.target.result);
reader.onerror = e => rej(e);
reader.readAsDataURL(file);
});
};
// for demo
const fileInput = document.createElement('input');
fileInput.type = 'file';
const img = document.createElement('img');
img.attributeStyleMap.set('max-width', '320px');
document.body.appendChild(fileInput);
document.body.appendChild(img);
const preview = async event => {
const file = event.target.files[0];
const url = await readURL(file);
img.src = url;
};
fileInput.addEventListener('change', preview);

$(function() {
// Multiple images preview in browser
var imagesPreview = function(input, placeToInsertImagePreview) {
if (input.files) {
var filesAmount = input.files.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
$($.parseHTML('<img>')).attr('src', event.target.result).appendTo(placeToInsertImagePreview);
}
reader.readAsDataURL(input.files[i]);
}
}
};
$('#gallery-photo-add').on('change', function() {
imagesPreview(this, 'div.gallery');
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple id="gallery-photo-add">
<div class="gallery">
$(function() {
// Multiple images preview in browser
var imagesPreview = function(input, placeToInsertImagePreview) {
if (input.files) {
var filesAmount = input.files.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
$($.parseHTML('<img>')).attr('src', event.target.result).appendTo(placeToInsertImagePreview);
}
reader.readAsDataURL(input.files[i]);
}
}
};
$('#gallery-photo-add').on('change', function() {
imagesPreview(this, 'div.gallery');
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple id="gallery-photo-add">
<div class="gallery">

Related

Load specific image to HTML file upload on button click

My script has an HTML file upload button in which I can upload an image by selecting any. I am creating functionality to load a specific image by clicking a button. Like if I click a button the HTML file upload value should load this URL image.
Image 1
https://studysciences.com/wp-content/uploads/2020/05/Osteoarthritis-main.jpg
var $btnLoadMaskImage = $('#input-mask-image-file');
var $btnApplyMask = $('#btn-apply-mask');
var $btnClose = $('.close');
$btnLoadMaskImage.on('change', function() {
var file;
var imgUrl;
if (!supportingFileAPI) {
alert('This browser does not support file-api');
}
file = event.target.files[0];
if (file) {
imgUrl = URL.createObjectURL(file);
imageEditor.loadImageFromURL(imageEditor.toDataURL(), 'FilterImage').then(function() {
imageEditor.addImageObject(imgUrl).then(function(objectProps) {
URL.revokeObjectURL(file);
console.log(objectProps);
});
});
}
});
$btnApplyMask.on('click', function() {
imageEditor.applyFilter('mask', {
maskObjId: activeObjectId
}).then(function(result) {
console.log(result);
});
});
$btnClose.on('click', function() {
imageEditor.stopDrawingMode();
$displayingSubMenu.hide();
});
<input type="file" accept="image/*" id="input-mask-image-file">
Working DEMO environment: https://codepen.io/tester2020/pen/ExPEyER?editors=1001
Essential code:
var $newBtn = $('#newBtn');
$newBtn.on('click', function() {
// URL address of your image:
var imgUrl = 'https://i.ibb.co/BPfJmqM/Osteoarthritis-main.jpg';
var byteNumbers = new Array(imgUrl.length);
for (var i = 0; i < imgUrl.length; i++) {
byteNumbers[i] = imgUrl.charCodeAt(i);
}
var file = new File(byteNumbers, imgUrl, { type: "image/jpeg" });
imageEditor.loadImageFromURL(imageEditor.toDataURL(), 'FilterImage').then(function() {
imageEditor.addImageObject(imgUrl).then(function(objectProps) {
URL.revokeObjectURL(file);
console.log(objectProps);
});
});
});

tf.browser.fromPixels returns all zeros from img element

I am using tensorflowjs to do some front-end image classification. I am trying to use tf.browser.fromPixels to convert an img element to a tensor. However, I am getting all zeros of shape [160, 160, 3]. I am using the FileReader api to read an image from the file system via the <input type="file"> element. Here's some of the code:
function getFiles(event) {
const files = event.target.files;
let tempStore = [];
for (let i = 0; i < files.length; ++i) {
tempStore.push(files[i]);
}
return tempStore;
}
const imageElement = document.getElementById("upload");
imageElement.addEventListener("change", event => {
const files = getFiles(event);
Promise.all(files.map(loadImg)).then(d => {
console.log("All done !!!", d);
});
});
const loadImg = imgFile => {
return new Promise((resolve, reject) => {
let reader = new FileReader();
let imgEl = document.createElement("img");
reader.onload = async e => {
imgEl.src = e.target.result;
imgEl.setAttribute("width", 160);
imgEl.setAttribute("height", 160);
document.body.append(imgEl);
const fromPixels = tf.browser.fromPixels(imgEl);
resolve(fromPixels);
};
reader.onerror = reject;
reader.readAsDataURL(imgFile);
});
};
The image gets appended to document body properly.
The imageElement is of the form:
<img src="data:image/jpeg;base64,....." width=160 height=160>
You are creating the tensor from the image when the img tag has not yet been loaded. Here is the way to go
imgEl.src = e.target.result;
imgEl.setAttribute("width", 160);
imgEl.setAttribute("height", 160);
document.body.append(imgEl);
im.onload = () => {
// create the tensor after the image has loaded
const fromPixels = tf.browser.fromPixels(imgEl);
resolve(fromPixels);
}

How to use the loop in the file input change event

Hello I have the following code
function fileValidation() {
var fileInput = document.getElementById('filech');
var filePath = fileInput.value;
var allowedExtensions = /(\.jpg|\.jpeg|\.png|\.gif)$/i;
if (!allowedExtensions.exec(filePath)) {
alert('error .jpeg/.jpg/.png/.gif ');
fileInput.value = '';
return false;
} else {
//Image preview
if (fileInput.files && fileInput.files[0]) {
var reader = new FileReader();
reader.onload = function(e) {
document.getElementById('imagePreview').innerHTML = '<img src="' + e.target.result + '"/>';
};
reader.readAsDataURL(fileInput.files[0]);
}
}
}
<input id="filech" type="file" name="file_img[]" multiple onchange="return fileValidation()" />
<div id="imagePreview"></div>
To upload photos by
<input id="filech" type="file" name="file_img[]" multiple onchange="return fileValidation()" />
then show
<div id="imagePreview"></div>
I want to show all the pictures and not one
How to use the loop here and thank all
Well as you said you will need a loop, the easiest way would be to use a for loop, like this:
for (var i = 0; i < fileInput.files.length; i++) {
if (fileInput.files && fileInput.files[i]) {
var reader = new FileReader();
reader.onload = function(e) {
document.getElementById('imagePreview').innerHTML += '<img src="' + e.target.result + '"/>';
};
reader.readAsDataURL(fileInput.files[i]);
}
}
Note:
Note that I changed it to document.getElementById('imagePreview').innerHTML +=, so it keep printing all the iterated images, otherwise it will just override the preview with the last image content.
But the best practice is to create an img element on each iteration and append it to the preview div:
for (var i = 0; i < fileInput.files.length; i++) {
if (fileInput.files && fileInput.files[i]) {
var reader = new FileReader();
reader.onload = function(e) {
var img = document.createElement("img");
img.src = e.target.result;
document.getElementById('imagePreview').appendChild(img);
};
reader.readAsDataURL(fileInput.files[i]);
}
}
Demo:
function fileValidation() {
var fileInput = document.getElementById('filech');
var filePath = fileInput.value;
var allowedExtensions = /(\.jpg|\.jpeg|\.png|\.gif)$/i;
if (!allowedExtensions.exec(filePath)) {
alert('error .jpeg/.jpg/.png/.gif ');
fileInput.value = '';
return false;
} else {
//Image preview
for (var i = 0; i < fileInput.files.length; i++) {
if (fileInput.files && fileInput.files[i]) {
var reader = new FileReader();
reader.onload = function(e) {
var img = document.createElement("img");
img.src = e.target.result;
document.getElementById('imagePreview').appendChild(img);
};
reader.readAsDataURL(fileInput.files[i]);
}
}
}
}
<input id="filech" type="file" name="file_img[]" multiple onchange="return fileValidation()" />
<div id="imagePreview"></div>

FileReader does not render the image from multiple files

I have this multiple type file input and then when onChange event is triggered unto the input file then it will loop through each file and then create a FileReader() and then render each file to an image but seems it only render the first one and not each file, any ideas, help please?
document.querySelector("input")
.onchange = function(e) {
for (var i = 0; i < e.target.files.length; i++) {
var img = document.createElement("img");
var reader = new FileReader();
reader.onload = function (e) {
img.src = e.target.result;
document.body.appendChild(img);
}
reader.readAsDataURL(e.target.files[i]);
}
}
img{
width:50px;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple><br><br><br>
FileReader returns results asynchronously. You can create a closure to use within for loop to process each file.
document.querySelector("input")
.onchange = function(e) {
for (var i = 0; i < e.target.files.length; i++) {
// use IIFE as a closure
(function(file) {
var img = document.createElement("img");
var reader = new FileReader();
reader.onload = function(e) {
img.src = e.target.result;
document.body.appendChild(img);
}
reader.readAsDataURL(file);
})(e.target.files[i]); // pass current File to closure
}
}
img {
width: 50px;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple><br><br><br>

set an onclick event watcher within an onchange event processing possible?

I saw a post How do I read in a local text file with javascript?
I want to add a button to simulate an upload. So my consideration is set a watcher to onclick in onchange processing, is it possible?
Here is jsfiddle
js
function readMultipleFiles(evt) {
//Retrieve all the files from the FileList object
var files = evt.target.files;
if (files) {
for (var i = 0, f; f = files[i]; i++) {
alert(f);
var r = new FileReader();
r.onload = (function (f) {
return function (e) {
var contents = e.target.result;
alert(contents);
};
})(f);
r.readAsText(f);
}
} else {
alert("Failed to load files");
}
}
document.getElementById('fileinput').addEventListener('change', readMultipleFiles, false);
html
<input type="file" id="fileinput" multiple />
Instead of the change handler, add a button and add a click handler
<input type="file" id="fileinput" multiple />
<button id="read">Read</button>
then
jQuery(function ($) {
function readMultipleFiles(input) {
//Retrieve all the files from the FileList object
var files = input.files;
if (files && files.length) {
for (var i = 0, f; f = files[i]; i++) {
var r = new FileReader();
r.onload = (function (f) {
return function (e) {
var contents = e.target.result;
alert(contents);
};
})(f);
r.readAsText(f);
}
} else {
alert("Failed to load files");
}
}
var fileIn = $('#fileinput')[0];
$('#read').click(function () {
readMultipleFiles(fileIn)
})
})
Demo: Fiddle

Categories