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HTML how to get canvas resource file?

The picture on the HTML page is represented as a canvas, but I have problems getting the source image name of this canvas, using javascript.
Page: https://www.futbin.com/22/squad-builder
I found this image in the page resources:
But how to get it programmically? I mean, if i have:
var canvas = document.getElementById('field-area')
How to get the file name? Result should be "field_1920x1080.png?v=8"

You can use HTMLCanvasElement.toDataURL to get the image drawn on the canvas base64 encoded
var canvas = document.getElementById('field-area');
var b64url = canvas.toDataURL('image/png');
This will return the url for the image itself, i don't think you can get the Asset name directly from a canvas element without inspecting the code on the website

EJBEAN is right, the canvas element doesn't know what resources were used to draw.
Why don't you use dataset to keep an eye on what you used?
var canvas = document.getElementById('field-area');
// ... draw resource here
canvas.dataset.resource = "field_1920x1080.png";
It's an easy way to keep data stored for any element on your page.

How to encrypt and decrypt image files online?

I'm working on a web application that involves loading images into a canvas object, then manipulating those images beyond recognition. I need to hide the original source image file (a jpeg) so that the user on the client side should not be able to use dev tools to see the original image.
I have tried to encode the images as a base64 and load it via a JSON data file, but even with this method, the inspector tool still shows the original image file (when it is set as the src of my javascript image object). Is there some way that I can encrypt and decrypt the image files, so that the user has no way of seeing the original image (or have it be some garbled image, for example)? Preferably I'd like to do this on the client side, as all my code is client side at the moment. Thanks in advance!
Here is my code for loading the base64 encoded image data via a JSON file:
//LOAD JSON INSTEAD?
$.getJSON( "media/masks.json", function( data ) {
console.log("media/masks.json LOADED");
//loop through data
var cnt = 0;
for (var key in data)
{
if (data.hasOwnProperty(key))
{
// here you have access to
//var id = key;
var imgData = data[key];
//create image object from data
var image = new Image();
image.src = imgData;
console.log('img src: '+ imgData);
var elementId = $scope.masks[cnt].id;
// copy the images to canvases
imagecanvas = document.createElement('CANVAS');
imagecanvas.width = image.width;
imagecanvas.height = image.height;
imagecanvas.getContext('2d').drawImage(image,0,0);
imageCanvases[elementId] = imagecanvas;
}
cnt++;
}
});
This is what I see in the Chrome dev tools Network inspector (exactly what I'm trying to avoid):

I need to hide the original source image file (a jpeg) so that the user on the client side should not be able to use dev tools to see the original image.
That's not possible. There is always a way to get at the image using developer tools. Even if there wasn't, a simple screen capture would defeat whatever measures you put in place.

Retrieving the absolute URL of a temporary canvas element on page

I created a coupon-creator system that uses HTML 5 canvas to spit out a jpg version of the coupon you create and since I'm not hosting the finalized jpg on a server, I am having trouble retrieving the URL. On some browsers when I drag the image into the address bar all I get is "data:" in the address bar. But on windows, if I drag it into an input field, sometimes it spits out the huge (>200 char) local-temp url. How can I use javascript(?) to find that exact temporary URL of the image generated by my coupon creator and be able to post it on an input form on the same page? Also, it'd be very helpful if you guys know the answer to this as well, as I assume it is correlated with the retrieval of the URL: When I click the link that says "Save it" after it's generated, how can I have it save the created image to the user's computer? Thanks a lot!
This is what I'm using in JS right now to generate the image:
function letsDo() {
html2canvas([document.getElementById('coupon')], {
onrendered: function (canvas) {
document.getElementById('canvas').appendChild(canvas);
var data = canvas.toDataURL('image/jpeg');
// AJAX call to send `data` to a PHP file that creates an image from the dataURI string and saves it to a directory on the server
var mycustomcoupon = new Image();
mycustomcoupon.src = data;
//Display the final product under this ID
document.getElementById('your_coupon').appendChild(mycustomcoupon);
document.getElementById('your_coupon_txt').style.display="block";
}
});
}
Here is the live URL of the creator: http://isleybear.com/coupon/

I ended up dumping this code into the js stated above. It was a pretty simple fix. Then to test it, I set an onclick html element to show the source.
var mycustomcoupon = document.getElementById('your_coupon');
mycustomcoupon.src = data;
}
});
}
function showSource(){
var source = document.getElementById('your_coupon').src;
alert(source);
}

Upload photo into facebook from html5 canvas

In my jsp page, I have a manipulated photo within a html5 canvas and I want to upload it to facebook upon clicking the upload button.
FacebookType publishPhotoResponse = facebookClient.publish("me/photos", FacebookType.class,
BinaryAttachment.with("test.jpeg", getClass().getResourceAsStream("xxx")),
Parameter.with("message", "Test"));
out.println("Published photo ID: " + publishPhotoResponse.getId());
I am using Restfb for the uploading part in my servlet. However, I have no clue what attribute is needed for me to pass over to servlet side for processing (for example: "xxx"). When I used toDataURL, the URL of the image is base64. Does facebook api allows me to upload photo using the base64 format?
var base64URL = document.getElementById('canvasImg').src;
var decodedURL = escape(window.atob(base64URL));
alert(decodedURL);
The above coding seems to contain error as it won't display the alert. Should I decode the base64 data first before handling it over to servlet or should I pass the whole base64 data to servlet to handle the decoding?

HTML5 - Attach image to mail using Java EE

I am developing an a drawing application using Javascript.
Users will be able to draw on a canvas. Once they are done with drawing, they will be able to convert it into an image (Convert to image button).
This is the code:
function putImage()
{
var canvas1 = document.getElementById("canvas");
if (canvas1.getContext)
{
var ctx = canvas1.getContext("2d");
var myImage = canvas1.toDataURL("image/png");
}
var imageElement = document.getElementById("MyPix");
imageElement.src = myImage;
$('#submit_btn').closest('.ui-btn').show();
}
There's a submit button and when the users click on it, the application will redirect to another page whereby the user will be able to send an email (using java mail) with the image attached to it.
The page allows user to type in the email address that they wanna send to, and the body of the email.
May i know how to make the image auto-attach to the email so that the after the user type in the email address and the body, they will be able to send the mail?
Thanks in advance!

To send the image as an attachment with javamail, you need the bytes from say a jpg or bmp. What you'll need to do is send the model, eg the coordinates, to the server and recreate the image server side. Perhaps a html5 canvas has direct support for outputting the images as bytes, I don't know, but that would help. In that case you'd simply transfer those bytes to the server for attaching to the mail.

HTML5 Canvas has a cool api trick to do this:
var encodedImage = canvas1.toDataURL(); //this generates base64 encoded image in png
//for jpeg
var encodedImage = canvas1.toDataURL("image/jpeg");
Now you can store that encodedImage in back-end in a table or file. If you want to show it on a page, just assign it back to html img tag to source property