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Preview an image before it is uploaded
(29 answers)
Closed 3 years ago.
<html>
<head><script src = "/jquery.js"></script></head>
Test Image Upload
<input type = "file" id = "chooseimage" name = "chooseimage" accept = ".jpg, .jpeg, .png" multiple><br>
<input type = "button" id = "submitimages" value = "Send Image">
<br>
<div id = "test"></div>
<script>
$("#submitimages").click(function(){
var imageinput = $("#chooseimage")[0].files[0];
var reader = new FileReader();
var a = reader.readAsDataURL(imageinput);
reader.onload = function(e)(){}; // what do i do with this?
$("#test").html(a);
});
</script>
</html>
For the Jquery, let me quickly run down my thought process.
1) I get the input id "chooseimage" and grab the files using .files command. I assume .files[0] means to select the first file from the HTML element (but it only selects it, not actually reading it)?
2) create a new FileReader(). I'm not quite sure what this does, I think it allows me to... read the file?
3) But to first read the file using FileReader, we need to convert the file to a base64 encoded string, so we use readAsDataURL to convert.
4) And then I do somrthing with reader.onload(), but I am not sure what this does. I was reading other tutorials on this and they all had it but no explanation what it does. I read the Mozilla Documentation but didn.t quite understand it. I've done nothing with it so far.
5) I want to show the base64 string in the div element with id "test". I think the browser will automatically interpret the string into an image. Either way, it's not showing anything.
Can someone walk me through what I do or do not understand correctly and what I'm doing wrong?
Check this out, and let me know how it goes. :)
function readURL(input) {
if (input.files && input.files[0]) {
var reader = new FileReader();
reader.onload = function(e) {
$('#imageShow').attr('src', e.target.result);
}
reader.readAsDataURL(input.files[0]);
}
}
$("#imgPreview").change(function() {
readURL(this);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form runat="server">
<input type='file' id="imgPreview" />
<img id="imageShow" src="#" alt="your image" />
</form>
Related
I am kind of new to Angular and right now I am trying to select multiple files and display their preview before uploading them to server.
My below code works fine if there are multiple files but selected separately, hovewer while trying to select multiple images at once, only the last one is rendered. I checked with console.log and while selecting multiple files at once the reader.result of the previous files except the last one is always null ever though the reader.onload is executing (the object is also inserted into the array, but without the image url).
I want to be able to also remove the selected files, so both files and their imagesUrl are kept in an FileWithImage object to keep the right order of their previews.
component.ts:
onFilesSelected(event: any): void {
this.selectedFiles = event.target.files;
for (let i = 0; i < this.selectedFiles.length; i++) {
let fileWithImage: FileWithImage = {
imageUrl: '',
file: this.selectedFiles[i],
};
var reader = new FileReader();
reader.readAsDataURL(fileWithImage.file);
reader.onload = (event) => {
fileWithImage.imageUrl = reader.result;
console.log(fileWithImage.file.name);
console.log(fileWithImage.imageUrl);
this.filesWithImages.push(fileWithImage);
};
}
}
component.html (selecting and displaying images):
<button
type="button"
mat-raised-button
(click)="fileInput.click()"
class="button"
>
Choose File
</button>
<input
hidden
(change)="onFilesSelected($event)"
#fileInput
type="file"
accept="image/*"
multiple="multiple"
/>
<div *ngFor="let file of filesWithImages" class="images">
<img
[src]="file.imageUrl"
height="10%"
width="10%"
*ngIf="file.imageUrl"
/>
</div>
I tried blocking the loop untill the reader.onload is executed with a use of a flag, but it did not work.
I also tried to get the url directly from a method:
createImageUrl(file: File): any {
var reader = new FileReader();
reader.readAsDataURL(file);
reader.onload = (event) => {
return reader.result;
};
}
and call it in [src] of an image tag in html, but it made my program crash.
The main problem is probably why the result of reader is null for the first few files and only the last one is properly displayed. Can someone help me to find the cause of this problem?
Try changing reader variable to local scope.
Change
var reader = new FileReader();
to
let reader = new FileReader();
I want to extract a string from a text file, convert it to a word scrambler (I figured out that part) and output it in another text file.
I found some code to input a text file and extract the text:
<html>
<h4>Select un file con .txt extension</h4>
<input type="file" id="myFile" accept=".txt" />
<br /><br />
<div id="output"></div>
<script>
var input = document.getElementById("myFile");
var output = document.getElementById("output");
input.addEventListener("change", function () {
if (this.files && this.files[0]) {
var myFile = this.files[0];
var reader = new FileReader();
reader.addEventListener("load", function (e) {
output.textContent = e.target.result;
});
reader.readAsText(myFile);
}
});
</script>
</html>
Input text and extract a text file
<html>
<div>
<input type="text" id="txt" placeholder="Write Here" />
</div>
<div>
<input type="button"id="bt"value="Save in a File"onclick="saveFile()"/>
</div>
<script>
let saveFile = () => {
const testo = document.getElementById("txt");
let data = testo.value;
const textToBLOB = new Blob([data], { type: "text/plain" });
const sFileName = "Testo.txt";
let newLink = document.createElement("a");
newLink.download = sFileName;
newLink.href = window.URL.createObjectURL(textToBLOB);
newLink.style.display = "none";
document.body.appendChild(newLink);
newLink.click();
};
</script>
</html>
But I don't know how to output a string in the first code or how to connect it to the second code. Could someone please show me how to do it or explain how these codes work so that I could try to do it myself in JavaScript?
I will comment each line of JavaScript, that should help you understand.
<script>
/*This creates a global variable with the HTML element input in it. */
var input = document.getElementById("myFile");
/*This creates a global variable with the HTML element div with id output in it. */
var output = document.getElementById("output");
/* this 2 lines are used to set the source and the destination.
The first will get where you put your file, in this case it's the input element.
The second will get the div which content will be replaced by the content of your txt file. */
/* Here we tell to our input element to do something special when his value changes.
A change will occur for example when a user will chose a file.*/
input.addEventListener("change", function () {
/* First thing we do is checking if this.files exists and this.files[0] aswell.
they might not exist if the change is going from a file (hello.txt) to no file at all */
if (this.files && this.files[0]) {
/* Since we can chose more than one file by shift clicking multiple files, here we ensure that we only take the first one set. */
var myFile = this.files[0];
/* FileReader is the Object in the JavaScript standard that has the capabilities to read and get informations about files (content, size, creation date, etc) */
var reader = new FileReader();
/* Here we give the instruction for the FileReader we created, we tell it that when it loads, it should do some stuff. The load event is fired when the FileReader reads a file. In our case this hasn't happened yet, but as soon as it will this function will fire. */
reader.addEventListener("load", function (e) {
/* What we do here is take the result of the fileReader and put it inside our output div to display it to the users. This is where you could do your scrambling and maybe save the result in a variable ? */
output.textContent = e.target.result;
});
/* This is where we tell the FileReader to open and get the content of the file. This will fire the load event and get the function above to execute its code. */
reader.readAsText(myFile);
}
});
</script>
With this I hope you'll be able to understand the first part of this code. Try putting the second part of your code instead of output.textContent and replacing data with e.target.result, that should do what you wish, but I'll let you figure it out by yourself first, comment on this answer if you need further help !
Here's a codepen with working and commented code:
https://codepen.io/MattDirty/pen/eYZVWyK
Id like to implement a UI where the user selects an image and that image is instantly displayed back to them for review. The user would have to click "submit" to upload/save the image to their profile.
I am having issues with the "instantly display back to the user part".
I am using angular FormData with the following markup & controller:
MARKUP
<input id="chooseFile" type="file" file-model="picFile" />
<img src="{{uploadedImage}}" /> <!-- this populates with filename but what is the path?? -->
CONTROLLER
angular.element('#chooseFile').change(function(){
var file = $scope.picFile; // this comes up "undefined" since file is still uploading when this is fired
$scope.uploadedImage = file.name;
});
I have 2 primary issues with the above code (described in comments):
1) In the controller, file comes up undefined obviously because even the smallest file takes >0s to upload while the callback is fired pretty much instantaneously. I got it work using $timeout but thats a bit of a lame hack. How can I have the callback wait until the file is uploaded??
2) The idea is to upload the file and display it in the img tag using Angular's data-binding. This works in that src is populated with the filename, but what is the path of the img. Some temporary location in cache or something?? Obviously I havent set a path to move the file yet.
Any help appreciated!
I also needed this feature, some how I manage to display image instantly.
angular.module('HelloWorldApp', [])
.controller('HelloWorldController', function($scope) {
$scope.uploadavtar = function(files) {
//var fd = new FormData();
//Take the first selected file
//fd.append("file", files[0]);
var imagefile = document.querySelector('#file');
if (imagefile.files && imagefile.files[0]) {
var reader = new FileReader();
reader.onload = function (e) {
$('#temp_image')
.attr('src', e.target.result);
};
reader.readAsDataURL(imagefile.files[0]);
this.imagefile = imagefile.files[0];
}else{
console.log("Image not selected");
}
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<div ng-app="HelloWorldApp">
<div ng-controller="HelloWorldController">
<input type="file" id="file" onchange="angular.element(this).scope().uploadavtar(this.files)"/>
</div>
<img src="" id="temp_image" width="100">
<div>
</div>
</div>
I was using laravel + Angularjs so another related post to store image is : https://stackoverflow.com/a/34830307/2815635
For context, I'm trying to create a "click image" file uploader. Initially there is a default image, which I then click. I trigger a file upload, and the user picks an image file they want. Then I will set the image to replace the default (and do other things with it later). Right now, the front end looks something like this:
<div class="right-preview">
<input type="image" src="img/logo.png" height="240px" width="240px" ng-click="uploadImage('right-image')" id="upload-right-image"/>
<input type="file" id="upload-right" style="visibility: hidden">
</div>
When the image is clicked, it triggers an upload action.
$scope.uploadImage = function(side) {
$image = $('#upload-' + side);
$fileInput = $('#upload-right');
$fileInput.change(function(changeEvent) {
var files = changeEvent.target.files;
for(var i = 0; i < files.length; i++) {
file = files[i];
console.log(file);
}
});
$fileInput.trigger('click');
}
When the change event is fired after the user finishes picking their file, I have the changeEvent and I know they've selected their file. Each of the files has some properties (like name and size) but I'm not seeing anything for accessing the raw data so I can set the src on my other element.
Am I just completely missing how to get the image data, or is there a better way to do this? I have no server (right now) to post this to. Perhaps there is a better way to approach this?
This link may be helpful to you - https://developer.mozilla.org/en-US/docs/Web/API/FileReader/readAsDataURL
I took one method from that page and added some additional functionality to hide the file upload button and have the image placeholder trigger its click event.
$('#placeholder').click(function() {
$('#img-upload').trigger('click');
});
function previewFile() {
var preview = document.querySelector('img');
var file = document.querySelector('input[type=file]').files[0];
var reader = new FileReader();
reader.addEventListener("load", function () {
preview.src = reader.result;
}, false);
if (file) {
reader.readAsDataURL(file);
}
}
.hidden {
display: none;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<img width="250" height="250" id="placeholder" src="http://place-hold.it/250x250&text='click to upload'">
<input class="hidden" type="file" onchange="previewFile()" id="img-upload">
I need to send selected image to the server, here is already I have tried
here is HTML part
<div class="row">
<input type="file" name="filUpload" id="filUpload" onchange="showimagepreview(this)">
<br />
<img id="imgprvw" alt="uploaded image preview" class="img-thumbnail" />
</div>
I need to get encoded image into javascript variable,But I have no idea
for uploading image on to server you need to send image data via AJAX to server side.
for reference you can see this link :
http://www.sanwebe.com/2012/05/ajax-image-upload-and-resize-with-jquery-and-php
http://phppot.com/php/php-ajax-image-upload/
you can try using jquery's base64 plugin. Jquery.Base64 plugin
and do it like this:
function showimagepreview(c) {
var file = c;
if(file.files.length)
{
var reader = new FileReader();
reader.onload = function(e)
{
var b = $.base64.encode(e.target.result);
$("#imgprvw").attr("src", "data:image/png;base64," + b);
};
reader.readAsBinaryString(file.files[0]);
}
}