I am trying to upload image on my website to add it to the database as base64 encoded string. The problem is I can not receive the file path to upload it by java. On the front-end I am using HTML and javascript, here is the HTML tag:
<div class="col-xs-6">
<label>passport image </label><input id="image-input" type="file"
placeholder="file">
</div>
in javascript I added:
document.getElementById("image-input").value;
The path of the image that arrives to me is 'C:\fakepath\IMAGE_NAME'.
I need a way to send the photo or it's path to the java code, how can I do this while I am not using jsf nor spring.
Some browsers have a security feature that prevents JavaScript from
knowing your file's local full path. It makes sense - as a client, you
don't want the server to know your local machine's filesystem.
I use the object FileReader on the input onchange event for your input
file type! This example uses the readAsDataURL function and for that
reason you should have an tag. The FileReader object also has
readAsBinaryString to get the binary data, which can later be used to
create the same file on your server
Example:
var input = document.getElementById("inputFile");
var fReader = new FileReader();
fReader.readAsDataURL(input.files[0]);
fReader.onloadend = function(event){
var img = document.getElementById("yourImgTag");
img.src = event.target.result;
}
try this ! using : replace
var imgpath = document.getElementById("image-input").value;
var newPath = imgpath .replace("C:\\fakepath\\", "")
I am trying to convert a canvas to image. The code used is as follows.
var canvas = document.getElementsByTagName("canvas")[0]
var context = canvas.getContext('2d');
url = canvas.toDataURL().replace(/^data:image\/[^;]/, 'data:application/octet-stream');
window.open(url);
The above code saves the image on the downloads folder. I need to save the image on a specific folder(Eg: /home/username/Desktop/projects/MyProject1/images/).
Any ideas on how this could be done?
I have a question about the File API and uploading files in JavaScript and how I should do this.
I have already utilized a file uploader that was quite simple, it simply took the files from an input and made a request to the server, the server then handled the files and uploaded a copy file on the server in an uploads directory.
However, I am trying to give people to option to preview a file before uploading it. So I took advantage of the File API, specifically the new FileReader() and the following readAsDataURL().
The file object has a list of properties such as .size and .lastModifiedDate and I added the readAsDataURL() output to my file object as a property for easy access in my Angular ng-repeat().
My question is, it occurred to me as I was doing this that I could store the dataurl in a database rather than upload the actual file? I was unsure if modifying the File data directly with it's dataurl as a property would affect its transfer.
What is the best practice? Is it better to upload a file or can you just store the dataurl and then output that, since that is essentially the file itself? Should I not modify the file object directly?
Thank you.
Edit: I should also note that this is a project for a customer that wants it to be hard for users to simply take uploaded content from the application and save it and then redistribute it. Would saving the files are urls in a database mitigate against right-click-save-as behavior or not really?
There is more then one way to preview a file. first is dataURL with filereader as you mention. but there is also the URL.createObjectURL which is faster
Decoding and encoding to and from base64 will take longer, it needs more calculations, more cpu/memory then if it would be in binary format.
Which i can demonstrate below
var url = 'https://upload.wikimedia.org/wikipedia/commons/c/cc/ESC_large_ISS022_ISS022-E-11387-edit_01.JPG'
fetch(url).then(res => res.blob()).then(blob => {
// Simulates a file as if you where to upload it throght a file input and listen for on change
var files = [blob]
var img = new Image
var t = performance.now()
var fr = new FileReader
img.onload = () => {
// show it...
// $('body').append(img)
var ms = performance.now() - t
document.body.innerHTML = `it took ${ms.toFixed(0)}ms to load the image with FileReader<br>`
// Now create a Object url instead of using base64 that takes time to
// 1 encode blob to base64
// 2 decode it back again from base64 to binary
var t2 = performance.now()
var img2 = new Image
img2.onload = () => {
// show it...
// $('body').append(img)
var ms2 = performance.now() - t2
document.body.innerHTML += `it took ${ms2.toFixed(0)}ms to load the image with URL.createObjectURL<br><br>`
document.body.innerHTML += `URL.createObjectURL was ${(ms - ms2).toFixed(0)}ms faster`
}
img2.src = URL.createObjectURL(files[0])
}
fr.onload = () => (img.src = fr.result)
fr.readAsDataURL(files[0])
})
The base64 will be ~3x larger. For mobile devices I think you would want to save bandwidth and battery.
But then there is also the latency of doing a extra request but that's where http 2 comes to rescue
I would like to be able to edit a file that has been selected for upload. I want to search and replace text in case absolute files should be made relative...
I notice in the File API I can do some of it, but I get a little stuck:
document.getElementById('exampleInputFile').onchange = function(event) {
var fileToLoad = event.target.files[0];
if (fileToLoad) {
var reader = new FileReader();
reader.onload = function(fileLoadedEvent) {
var textFromFileLoaded = fileLoadedEvent.target.result;
//Use logic to remove absolute files
//Upload S3
};
reader.readAsText(fileToLoad, 'UTF-8');
}
};
I am trying to figure out how now to convert that text to a proper File so that I can upload it to S3 using an existing api that expects something returned by: event.target.files[0] code above.
I do not want the server to handle any heavy lifting here if I can avoid it (files can easily be a few megabytes since they can be 3D models).
Assuming you know the url of the file when it lands in the S3 bucket, you can retrieve the file using a http.get, which will give you the contents of the (I assume plain text file). You can then parse that file and do whatever modification you need to do on the contents. If the file has changed, you can then write it back to the S3 bucket to replace the original file.
On AWS you can use Lambda to execute NodeJS code when an event is triggered (for example an upload to a specified bucket).
I have an image encoded in base64 in a javascript variable : data:image/png;base64, base64 data
[EDIT]
I need to save that file to disk without asking to the visitor to do a right click
[/EDIT]
Is it possible ? How ?
Thanks in advance
Best regards
I know this question is 2 years old, but hopefully people will see this update.
You can prompt the user to save an image in a base64 string (and also set the filename), without asking the user to do a right click
var download = document.createElement('a');
download.href = dataURI;
download.download = filename;
download.click();
Example:
var download = document.createElement('a');
download.href = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
download.download = 'reddot.png';
download.click();
In order to trigger a click event using Firefox, you need to do what it is explained in this SO answer. Basically:
function fireEvent(obj,evt){
var fireOnThis = obj;
if(document.createEvent ) {
var evObj = document.createEvent('MouseEvents');
evObj.initEvent( evt, true, false );
fireOnThis.dispatchEvent( evObj );
} else if( document.createEventObject ) {
var evObj = document.createEventObject();
fireOnThis.fireEvent( 'on' + evt, evObj );
}
}
fireEvent(download, 'click')
As of 20/03/2013, the only browser that fully supports the download attribute is Chrome. Check the compatibility table here
... without asking to the visitor anyhing ... Is it possible?
No, that would have been a security hole. If it was possible, one would be able to write malware to the enduser's disk unaskingly. Your best bet may be a (signed) Java Applet. True, it costs a bit of $$$ to get it signed (so that it doesn't pop security warnings), but it is able to write data to enduser's disk without its permission.
I am surprised nobody here mentioned using HTML5 blobs together with a couple of nice libraries.
You first need https://github.com/eligrey/FileSaver.js/ and https://github.com/blueimp/JavaScript-Canvas-to-Blob.
Then you can load the image into a canvas
base_image = new Image();
base_image.src ='data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
the canvas into a blob
var canvas = document.getElementById('YourCanvas');
context = canvas.getContext('2d');
// Draw image within
context.drawImage(base_image, 0,0);
and finally save it
x_canvas.toBlob(function(blob) {
saveAs(blob, "screenshot.png");
}, "image/png");
FF is not fully supported but at least you get a separate page with the image.
Check this out: http://jsfiddle.net/khhmm/9/
EDIT: this is not compatible with Safari / Mac.
As other answers already stated, you cannot do it only with javascript. If you want, you can send the data (using normal HTTP POST) to a PHP script, call header('Content-type: image/png') and output the decoded image data to the page using echo base64_decode($base64data).
This will work just as if user clicked on an image and open it or prompt him to save the file to disk (the normal browser's save file dialog).
It's not possible.
If it was, browsers would be massively insecure, being able to write random data to your hard disk without user interaction.
with javascript, you can't. the only real possibility i can think of will be a java-applet, but maybe (i don't know how long that image should be saved) you could simply add an img-tag with you png and force caching (but if the user deletes his cache, the image will be gone).
I think it's possible with JavaScript if you use ActiveX.
Another possibility is to make the server spit out that file with a different mime type so the browser asks the user to save it.
I think you can do it something(maybe not only with javascript...xul programming needed). There are Firefox addons that save images to a folder(check Firefox addons site)
You can make this file as blob on the server and use setTimeout function in order to fire the download.
The accepted solution seems to have a limitation for large data. If you're running into this (instead of the downloaded file's name, I see "download" and "Failed - Network error" in Chrome), here's what I did in order to download a 2mb file:
const blob = await (await fetch(document.getElementById('canvasID').toDataURL())).blob();
const file = new File([blob], {type:"image/png", lastModified: new Date()});
var a = document.createElement('a');
a.href = window.URL.createObjectURL(file);
a.download = 'image.png';
a.click();