loading an image through javascript - javascript

is there a way to load the full binary of an image in javascript?
what i want to do is to allow the user to preview an image before uploading it.
ie the user selects an image on his local drive (C:\image.jpg) , view it, and decides to upload or cancel.
i tried to set the source to the image path, but it didn't work since it is outside the webapplication project folder.
any help?

thx for your posts, but i ended up creating a temp folder on the server that stores the uploaded image using ajax. and when the user saves the data, the image is moved to another location, and the temp folder is deleted.

You can do something like this:
<img id="preview" src="" style="display:none;" />
<form>
....
<input type="file" id="file" />
....
</form>
<script type="text/javascript">
var file = document.getElementById("file");
var img = document.getElementById("preview");
file.onchange = function(){
img.src = file.value;
img.style.display = 'block';
};
</script>

There is no easy way, what You could do:
Preload image with some ajax file uploader to temp area and then let user decide
Use some third party written solution (f.ex. some flash component)
Here there is also similar question:
is it possible to preview local images before uploading them via a form?

You need server cooperation to access the image binary data. You won't be able to use the "Upload Form" to access the file info without uploading it to a server.
You could however do something like tell the user to paste the source binary data of the image in a textarea or something, then you can use JavaScript to load that binary data and display the actual image.

This is available in some browsers via the HTML5 file access API. Here is the Firefox documentation for file access.

As answered several times, you can't do this with plain HTML/JavaScript due to security restrictions. You need to send the image anyway. You can however handle this using a Java Applet since it runs entirely at the client machine and offers more control than HTML/JS. There are several free and ready-to-use ones. JumpLoader looks good and some major sites also uses it. With Flash it should also be possible, but I am not sure which ones offers this functionality. Check/tryout some Flash Multi File Uploaders.

Related

Saving user uploaded image to folder and/or server

I have an app, that allows users to upload an image, crop it and with other data save it all as html file to be used as a footer for emails. The image is given to them as base64.
Howver turns out this is not supported by Outlook, since it doesnt accept b64 data as img source.
So my idea was to save the cropped image to a file, let's say /public/avatars/avatar.png and link it's directory as a source. However I'm having trouble finding a way how to save images to to a file using JS. My allowed stack is JS and React, no node.js.
How would I do that? I can have the file as either b64 ot canvas element, so i'm flexible here, as long as it's saved to file.
I'm open to other solutions too.
You can't save a file with client language only. You have to save it to a server, own server or external server or a service like AWS.
The best solution without server-side (strangly) is to use a API for save image and get link from this API. Then you can use this link to Outlook.
You can use https://aws.amazon.com/fr/cloudfront/ free for one year with 50Go and 2 millon request monthly.
If you do not exceed 300,000 images per year you can use this service : https://cloudinary.com/pricing
You can also use https://www.deviantart.com/developers/ but that's not really the point of service.
Weird solution :
Be careful, the login and password of your FTP user will be available in the source of your code. Minimum rights must be administered.
You can use this script for talk to FTP server from JS (not tested but seems worked) : http://www.petertorpey.com/files/ae/scripts/FTPConnection.jsx
You can try something like that :
var ftp = new FtpConnection("ftp://URL") ;
ftp.login("username", "password");
ftp.cd("FOLDER") // For move to folder
ftp.put(file,"FILE.PNG") ; // File must be a File JS Object
ftp.close() ;

Upload file with input[type="file"] without a second button to send

I'm setting up a typical profile picture upload and crop feature for a site. I'm looking at how others have set it up and I see that many are managing to have one input type="file" and it not only allows for selecting a file but also calls the PHP or JS to display the image.
I'm completely stuck on how to make it do something after the image has been chosen.
Does any one have a link or suggestion on how to perform this?
One way you could achieve this is to convert the file into a blob, then present it using an HTML5 canvas. Example: http://www.html5rocks.com/en/tutorials/file/dndfiles/
Another option is to issue an AJAX request after the file input has been changed. Do whatever server processing you need to (crop, save, etc.) then return the AJAX call a path to the file. Then just append a new <img src='filepath.jpg' /> to the DOM.
I would upload the image using AJAX, having a API receiving the image. When image has been saved the API-method returns the path of the image.
You can then display the image using the path you recieved from your API-method.

How to post a file to a form using javascript automatically

I have some client-side JavaScript which will output a jpeg file based on HTML5 canvas manipulation, if the user performs an action such as clicking the "OK" button.
I would like the jpeg output to be automatically loaded into the "Upload Front Side" field in a form, as if the user uploaded the file from his or her own hard drive.
However, I can't seem to get it to work.
Here is the form:
<div class="property-wrapper">
<label for="upload-front">Upload Front Side</label>
<input id="upload" class="file" type="file" enctype="multipart/form-data" id="Front-Side" name="properties[Front Side]" onchange="readURL(this);" accept="image/*" />
</div>
<script>
document.getElementById('upload').value="http://upload.wikimedia.org/wikipedia/commons/thumb/2/22/Turkish_Van_Cat.jpg/353px-Turkish_Van_Cat.jpg"
</script>
The problem is browsers have several restrictions on what can be done programatically with file upload due to security reasons, have a look at this answer.
The file upload functionality is potentially exploitable, and some browsers will for example not open the explorer box if for example the file upload input field is hidden with display:none.
Most browsers will not allow programatic clicks to a file upload element and require the user to click them instead, to prevent attacks where someone sends a link to a page that immediately steals content from the user's hard drive.
So the functionality you mention does not seem to be feasible due to common browser security restrictions. There are usually no error messages or warnings, it just doesn't work.
An alternative to using the file upload browser input component could be to encode the contents of the file in Base64 and send in the body of an ajax POST for example.
Are you asking how to upload to a server, via a form, the graphic image you extracted from the canvas of your page? This would be useful, I hope to see this answered.
I would start by enabling the user to download/export the image. This might be done with a blob. Ive done this for text data exports, works nicely.
Maybe there is a way to apply the same tricks, just feed the blob/buffer to the server.
Another path might be to "PUT" the file at the server.
Hope this helps.
I would ajax POST a base64 encoded string of the image and forget the whole file upload thingy. You can upload the canvas code directly and reconvert it server side if you need a preview or something or see what other outputs are available from your canvas/image converter code.
I am assuming you are uploading to same server so you would not have cross domain issue but otherwise you can setup your server to accept cross domain ajax request very easily.

How to load images from the local machine to JS object avoiding loading to the server

I want to load an image file from the computer directly to any js object without using any server-side component. For example, I want to select a picture from the local machine and display it on a webpage. Is there a way to avoid file upload to the server?
In fact I want to write a kind of multiple image loader, but before loading to the server I want to rotate some images, create an xml-file with some data like user id, image file names list and to zip all images and this xml and then send it to the server. How can I do that on the client side?
There is a way with HTML5, but it requires the user to have dropped the file into a drop target or used a <input type="file"/> box, since otherwise it would be a security issue.
Using the File API you can read files, and specifically you can use the FileReader.readAsDataURL method to set the content as a data: URL for the image tag.
Here's an example:
$('#f').on('change', function(ev) {
var f = ev.target.files[0];
var fr = new FileReader();
fr.onload = function(ev2) {
console.dir(ev2);
$('#i').attr('src', ev2.target.result);
};
fr.readAsDataURL(f);
});​
http://jsfiddle.net/alnitak/Qszjg/
Using the new File APIs, it is possible to access content from the local disk.
You put a traditional <input type="file"> upload field on your page, and handle the onchange event.
MDN has a good writeup with all of the details.
Your event handler gets a FileList containing Files. From there, you can call FileReader.readAsDataURL(File) to fetch the content of the image and then pass that data URL to an <img> or a <canvas> to do rotation.
You can use createObjectURL method of the window.URL object, this doesn't have much browser support though
http://jsfiddle.net/LvAqp/ only works in chrome and firefox

How do I open a file stream in javascript?

To give a concrete example of what I mean:
Imagine I have an HTML page that looks like this
<div>
<div id="filecontents">
<!-- some html file contents -->
</div>
<input type="button" />
</div>
I would like to be able to click on the button, and it bring me up with a "Open or save file" dialog box.
Is this even possible?
The objective of this is, is for me to be able to open up some html, text, or a CSV using the contents of a div as a data source for the file.
You can do this using the HTML5 FileSystem APIs. A couple tutorials here:
Reading local files in JavaScript
Exploring the FileSystem APIs
Browser support is weak right now, but my guess is that it's the closest to what you want.
doesn't <input type="file" /> do that exact thing?
I don't understand all these answers that say this is not possible without a plugin. I would say it absolutely is possible with standard web technologies, but requires user interaction and server interaction. Of course you can't go reading or writing whatever you want on a user's computer from the web, but you can ask a user for a file (open), and give a user a file (save).
To open a file with JavaScript, use a <input type="file" />. If you want, you can use JavaScript to display the open dialog by calling the click() method on the file input (the DOM method, not the jQuery method). In the onchange handler, submit the form, read the uploaded file, and write the contents to your page.
To save a file with JavaScript, send the contents of the file to the server, prepare the file, and stream it back to the client with a content-disposition header of attachment; filename="file.txt". This header causes the file to be downloaded and saved the user's pc rather than displayed in the browser.
Do that and you've officially written your first cloud computing app!
<input type="file" /> will allow you to upload a file to the server, but you have no direct access to that file, or to the local file system, from javascript - this is a security feature.
If you want to alter the page somehow based on the contents of the file, you will have to do a round-trip: upload the file to the server, then render a new page with the changes you want, and send it back to the client.
I have seen some file-stream-like code written for javascript (i.e., a flash implementation), but they must "load" files via an ajax request and then read the data as a javascript string.
You cannot access the local filesystem from javascript because of security reasons. You can, however, receive files via drag and drop in modern browsers or use an java applet that communicates with your javascript.
EDIT: forgot about the new HTML5 file api linked by Michael Mior. Go with his answer, he's the man. If you need cross browser support, go with the java applet, its painful but works.
Not with pure JavaScript. You can't open a file dialog to save part of the HTML, for example. Even if you could, there is no way to open a local file with JavaScript for security reasons (otherwise, malicious web sites could steal all your data).
But every browser allows to write plugins (most of them are written in JavaScript), so you could try this approach.
Use this script and put it in the button that the file browser should display.
function handleFileSelect(evt) {
var files = evt.target.files;
for (var i = 0, f; f = files[i]; i++) {
if (!f.type.match('image.*')) {
continue;
}
var reader = new FileReader();
reader.onload = (function(theFile) {
return function(e) {
var span = document.createElement('span');
span.innerHTML = ['<img class="thumb" src="', e.target.result, '"
title = "', escape(theFile.name), '" / > '].join('
');
document.getElementById('list').insertBefore(span, null);
};
})(f); reader.readAsDataURL(f);
}
}
document.getElementById('files').addEventListener('change', handleFileSelect, false);

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