How to handle downloading external images using html2canvas? - javascript

I have a page with several book covers and a button to download them all.
Book covers are in String format and are a Google Books URL. I'm populating like this:
<section ref="capture" id="my-node">
<figure v-for="book in books" :key="book.id">
<img :src="book.thumbnail" :alt="`Book ${book.title}`" />
</figure>
<button type="button" #click="download">html2canvas</button>
</section>
To download the book covers I'm calling the following function:
download() {
html2canvas(this.$refs["capture"], { allowTaint: true })
.then((canvas) => {
let link = document.createElement("a");
link.download = "Livrero.png";
link.href = canvas.toDataURL("image/png");
link.click();
})
},
Books is an object that contains a thumbnail property with values like this: https://books.google.com/books/content?id=_i6bDeoCQzsC&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api
What makes me more confused is that if I were using values similar to this: https://images-na.ssl-images-amazon.com/images/I/41xShlnTZTL._SX218_BO1,204,203,200_QL40_FMwebp_.jpg everything would be working, but unfortunately the project does not allow this at the moment.
Previously I was using the property useCORS: true in html2canvas however it was returning a CORS policy error. So, when I removed it, I stopped having this error and started getting the following error:
DOMException: Failed to execute 'toDataURL' on 'HTMLCanvasElement':
Tainted canvases may not be exported.
It was suggested that I use http://html2canvas.hertzen.com/proxy/ to succeed in the mission, but because I'm using Vue.js I don't know how to apply this.

This is a problem with browser's content policy. There is no simple solution.
The browser won't let you use content (images) from different origins which don't explicitly allow it.
With useCORS: true, it's expected that the server (with the remote resource) responds with the appropriate access-control-allow-origin headers. Your Amazon link does, that's why it works.
With allowTaint: true, it accepts the image, but then refuses to let you do anything with the resulting canvas image as it's now considered tainted.
Since you can't make 3rd party server send appropriate CORS headers, you will have to run your own CORS proxy.
To run html2canvas-proxy mentioned in the official documentation you need to install it
npm install html2canvas-proxy --save
make a start JavaScript file
var proxy = require('html2canvas-proxy');
var express = require('express');
const port = 8000;
var app = express();
app.use('/', proxy());
app.listen(port, () => {
console.log(`html2canvas-proxy listening on port ${port}`)
})
and then use the proxy option in html2canvas
html2canvas(this.$refs["capture"], {
proxy: "http://localhost:8000",
})
.then((canvas) => {
// ...
})
But for production, this simple proxy isn't good either as it allows anyone to use is as a CORS proxy and you might not want a separate server, if you aren't not already running an Express Node.js server.

Related

How to make a custom url for a file in electron

I am trying to build a mini browser using Electron.js. Is it possible to make urls like chrome://settings or about:config, so that when the user goes to that link I can show an html file? I basically want to associate a url with a file in electron.
You could use Data URIs, and base64-encode the contents of your data as a link. You can use Javascript to encode and decode binary data, then you just specify the MIME type at the start.
If you go to the following URL in a browser for example you'll see a png decoded and rendered:
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==
The MDN Web doc in the first link mentions the process of base64 encoding an HTML file.
Alternatively, if you just want to force the download of a link you could add the download attribute to your anchor.
You can use did-start-navigation to detect when they go to chrome://settings/ then intercept that and tell it to go to https://stackoverflow.com/ instead.
Here's the code:
mainWin.webContents.on('did-start-navigation', function (evt, navigateUrl) {
if (navigateUrl == 'chrome://settings/') {
evt.preventDefault();
setTimeout(function () { // Without this it just crashes, no idea why.
mainWin.loadURL('https://stackoverflow.com/');
}, 0);
}
});
I tried the `will-navigate` event, but it didn't work.
Docs for: did-start-navigation
After a little searching at npm, I found a package that does exactly what I want, it's electron protocols. It's a simple way to add custom protolcs in Electron, Here's an example"
const protocols = require('electron-protocols');
const path = require('path');
protocols.register('browser', uri => {
let base = app.getAppPath();
if(uri.hostname == "newtab"){
return path.join(base,"newtab.html")
}
});
In this example, if you go to the link browser://newtab, it opens newtab.html. And if you type location.href the DevTools it shows browser://newtab there too

Tampermonkey To open multiple javascript in href in new tab [duplicate]

Over the years on snapchat I have saved lots of photos that I would like to retrieve now, The problem is they do not make it easy to export, but luckily if you go online you can request all the data (thats great)
I can see all my photos download link and using the local HTML file if I click download it starts downloading.
Here's where the tricky part is, I have around 15,000 downloads I need to do and manually clicking each individual one will take ages, I've tried extracting all of the links through the download button and this creates lots of Urls (Great) but the problem is, if you past the url into the browser then ("Error: HTTP method GET is not supported by this URL") appears.
I've tried a multitude of different chrome extensions and none of them show the actually download, just the HTML which is on the left-hand side.
The download button is a clickable link that just starts the download in the tab. It belongs under Href A
I'm trying to figure out what the best way of bulk downloading each of these individual files is.
So, I just watched their code by downloading my own memories. They use a custom JavaScript function to download your data (a POST request with ID's in the body).
You can replicate this request, but you can also just use their method.
Open your console and use downloadMemories(<url>)
Or if you don't have the urls you can retrieve them yourself:
var links = document.getElementsByTagName("table")[0].getElementsByTagName("a");
eval(links[0].href);
UPDATE
I made a script for this:
https://github.com/ToTheMax/Snapchat-All-Memories-Downloader
Using the .json file you can download them one by one with python:
req = requests.post(url, allow_redirects=True)
response = req.text
file = requests.get(response)
Then get the correct extension and the date:
day = date.split(" ")[0]
time = date.split(" ")[1].replace(':', '-')
filename = f'memories/{day}_{time}.mp4' if type == 'VIDEO' else f'memories/{day}_{time}.jpg'
And then write it to file:
with open(filename, 'wb') as f:
f.write(file.content)
I've made a bot to download all memories.
You can download it here
It doesn't require any additional installation, just place the memories_history.json file in the same directory and run it. It skips the files that have already been downloaded.
Short answer
Download a desktop application that automates this process.
Visit downloadmysnapchatmemories.com to download the app. You can watch this tutorial guiding you through the entire process.
In short, the app reads the memories_history.json file provided by Snapchat and downloads each of the memories to your computer.
App source code
Long answer (How the app described above works)
We can iterate over each of the memories within the memories_history.json file found in your data download from Snapchat.
For each memory, we make a POST request to the URL stored as the memories Download Link. The response will be a URL to the file itself.
Then, we can make a GET request to the returned URL to retrieve the file.
Example
Here is a simplified example of fetching and downloading a single memory using NodeJS:
Let's say we have the following memory stored in fakeMemory.json:
{
"Date": "2022-01-26 12:00:00 UTC",
"Media Type": "Image",
"Download Link": "https://app.snapchat.com/..."
}
We can do the following:
// import required libraries
const fetch = require('node-fetch'); // Needed for making fetch requests
const fs = require('fs'); // Needed for writing to filesystem
const memory = JSON.parse(fs.readFileSync('fakeMemory.json'));
const response = await fetch(memory['Download Link'], { method: 'POST' });
const url = await response.text(); // returns URL to file
// We can now use the `url` to download the file.
const download = await fetch(url, { method: 'GET' });
const fileName = 'memory.jpg'; // file name we want this saved as
const fileData = download.body; // contents of the file
// Write the contents of the file to this computer using Node's file system
const fileStream = fs.createWriteStream(fileName);
fileData.pipe(fileStream);
fileStream.on('finish', () => {
console.log('memory successfully downloaded as memory.jpg');
});

Redirect from php file to a local HTML file [duplicate]

Test browser:
Version of Chrome: 52.0.2743.116
It is a simple javascript that is to open an image file from local like 'C:\002.jpg'
function run(){
var URL = "file:///C:\002.jpg";
window.open(URL, null);
}
run();
Here is my sample code.
https://fiddle.jshell.net/q326vLya/3/
Please give me any suitable suggestions.
We use Chrome a lot in the classroom and it is a must to working with local files.
What we have been using is "Web Server for Chrome". You start it up, choose the folder wishing to work with and go to URL (like 127.0.0.1:port you chose)
It is a simple server and cannot use PHP but for simple work, might be your solution:
https://chrome.google.com/webstore/detail/web-server-for-chrome/ofhbbkphhbklhfoeikjpcbhemlocgigb
1)
Open your terminal and type
npm install -g http-server
2)
Go to the root folder that you want to serve you files and type:
http-server ./
3)
Read the output of the terminal, something kinda http://localhost:8080 will appear.
Everything on there will be allowed to be got.
Example:
background: url('http://localhost:8080/waw.png');
Okay folks, I completely understand the security reasons behind this error message, but sometimes, we do need a workaround... and here's mine. It uses ASP.Net (rather than JavaScript, which this question was based on) but it'll hopefully be useful to someone.
Our in-house app has a webpage where users can create a list of shortcuts to useful files spread throughout our network. When they click on one of these shortcuts, we want to open these files... but of course, Chrome's error prevents this.
This webpage uses AngularJS 1.x to list the various shortcuts.
Originally, my webpage was attempting to directly create an <a href..> element pointing at the files, but this produced the "Not allowed to load local resource" error when a user clicked on one of these links.
<div ng-repeat='sc in listOfShortcuts' id="{{sc.ShtCut_ID}}" class="cssOneShortcutRecord" >
<div class="cssShortcutIcon">
<img ng-src="{{ GetIconName(sc.ShtCut_PathFilename); }}">
</div>
<div class="cssShortcutName">
<a ng-href="{{ sc.ShtCut_PathFilename }}" ng-attr-title="{{sc.ShtCut_Tooltip}}" target="_blank" >{{ sc.ShtCut_Name }}</a>
</div>
</div>
The solution was to replace those <a href..> elements with this code, to call a function in my Angular controller...
<div ng-click="OpenAnExternalFile(sc.ShtCut_PathFilename);" >
{{ sc.ShtCut_Name }}
</div>
The function itself is very simple...
$scope.OpenAnExternalFile = function (filename) {
//
// Open an external file (i.e. a file which ISN'T in our IIS folder)
// To do this, we get an ASP.Net Handler to manually load the file,
// then return it's contents in a Response.
//
var URL = '/Handlers/DownloadExternalFile.ashx?filename=' + encodeURIComponent(filename);
window.open(URL);
}
And in my ASP.Net project, I added a Handler file called DownloadExternalFile.aspx which contained this code:
namespace MikesProject.Handlers
{
/// <summary>
/// Summary description for DownloadExternalFile
/// </summary>
public class DownloadExternalFile : IHttpHandler
{
// We can't directly open a network file using Javascript, eg
// window.open("\\SomeNetworkPath\ExcelFile\MikesExcelFile.xls");
//
// Instead, we need to get Javascript to call this groovy helper class which loads such a file, then sends it to the stream.
// window.open("/Handlers/DownloadExternalFile.ashx?filename=//SomeNetworkPath/ExcelFile/MikesExcelFile.xls");
//
public void ProcessRequest(HttpContext context)
{
string pathAndFilename = context.Request["filename"]; // eg "\\SomeNetworkPath\ExcelFile\MikesExcelFile.xls"
string filename = System.IO.Path.GetFileName(pathAndFilename); // eg "MikesExcelFile.xls"
context.Response.ClearContent();
WebClient webClient = new WebClient();
using (Stream stream = webClient.OpenRead(pathAndFilename))
{
// Process image...
byte[] data1 = new byte[stream.Length];
stream.Read(data1, 0, data1.Length);
context.Response.AddHeader("Content-Disposition", string.Format("attachment; filename={0}", filename));
context.Response.BinaryWrite(data1);
context.Response.Flush();
context.Response.SuppressContent = true;
context.ApplicationInstance.CompleteRequest();
}
}
public bool IsReusable
{
get
{
return false;
}
}
}
And that's it.
Now, when a user clicks on one of my Shortcut links, it calls the OpenAnExternalFile function, which opens this .ashx file, passing it the path+filename of the file we want to open.
This Handler code loads the file, then passes it's contents back in the HTTP response.
And, job done, the webpage opens the external file.
Phew ! Again - there is a reason why Chrome throws this "Not allowed to load local resources" exception, so tread carefully with this... but I'm posting this code just to demonstrate that this is a fairly simple way around this limitation.
Just one last comment: the original question wanted to open the file "C:\002.jpg". You can't do this. Your website will sit on one server (with it's own C: drive) and has no direct access to your user's own C: drive. So the best you can do is use code like mine to access files somewhere on a network drive.
Chrome specifically blocks local file access this way for security reasons.
Here's an article to workaround the flag in Chrome (and open your system up to vulnerabilities):
http://www.chrome-allow-file-access-from-file.com/
There is a workaround using Web Server for Chrome. Here are the steps:
Add the Extension to chrome.
Choose the folder (C:\images) and launch the server
on your desired port.
Now easily access your local file:
function run(){
// 8887 is the port number you have launched your serve
var URL = "http://127.0.0.1:8887/002.jpg";
window.open(URL, null);
}
run();
PS: You might need to select the CORS Header option from advanced setting incase you face any cross origin access error.
This issue come when I am using PHP as server side language and the work around was to generate base64 enconding of my image before sending the result to client
$path = 'E:/pat/rwanda.png';
$type = pathinfo($path, PATHINFO_EXTENSION);
$data = file_get_contents($path);
$base64 = 'data:image/' . $type . ';base64,' . base64_encode($data);
I think may give someone idea to create his own work around
Thanks
Google Chrome does not allow to load local resources because of the security. Chrome need http url. Internet Explorer and Edge allows to load local resources, but Safari, Chrome, and Firefox doesn't allows to load local resources.
Go to file location and start the Python Server from there.
python -m SimpleHttpServer
then put that url into function:
function run(){
var URL = "http://172.271.1.20:8000/" /* http://0.0.0.0:8000/ or http://127.0.0.1:8000/; */
window.open(URL, null);
}
If you have php installed - you can use built-in server. Just open target dir with files and run
php -S localhost:8001
If you could do this, it will represent a big security problem, as you can access your filesystem, and potentially act on the data available there... Luckily it's not possible to do what you're trying to do.
If you need local resources to be accessed, you can try to start a web server on your machine, and in this case your method will work. Other workarounds are possible, such as acting on Chrome settings, but I always prefer the clean way, installing a local web server, maybe on a different port (no, it's not so difficult!).
See also:
Open local files(file://) using Chrome
Opening local files from chrome
You just need to replace all image network paths to byte strings in stored Encoded HTML string.
For this you required HtmlAgilityPack to convert Html string to Html document.
https://www.nuget.org/packages/HtmlAgilityPack
Find Below code to convert each image src network path(or local path) to byte sting.
It will definitely display all images with network path(or local path) in IE,chrome and firefox.
string encodedHtmlString = Emailmodel.DtEmailFields.Rows[0]["Body"].ToString();
// Decode the encoded string.
StringWriter myWriter = new StringWriter();
HttpUtility.HtmlDecode(encodedHtmlString, myWriter);
string DecodedHtmlString = myWriter.ToString();
//find and replace each img src with byte string
HtmlDocument document = new HtmlDocument();
document.LoadHtml(DecodedHtmlString);
document.DocumentNode.Descendants("img")
.Where(e =>
{
string src = e.GetAttributeValue("src", null) ?? "";
return !string.IsNullOrEmpty(src);//&& src.StartsWith("data:image");
})
.ToList()
.ForEach(x =>
{
string currentSrcValue = x.GetAttributeValue("src", null);
string filePath = Path.GetDirectoryName(currentSrcValue) + "\\";
string filename = Path.GetFileName(currentSrcValue);
string contenttype = "image/" + Path.GetExtension(filename).Replace(".", "");
FileStream fs = new FileStream(filePath + filename, FileMode.Open, FileAccess.Read);
BinaryReader br = new BinaryReader(fs);
Byte[] bytes = br.ReadBytes((Int32)fs.Length);
br.Close();
fs.Close();
x.SetAttributeValue("src", "data:" + contenttype + ";base64," + Convert.ToBase64String(bytes));
});
string result = document.DocumentNode.OuterHtml;
//Encode HTML string
string myEncodedString = HttpUtility.HtmlEncode(result);
Emailmodel.DtEmailFields.Rows[0]["Body"] = myEncodedString;
Chrome and other Browser restrict the access of a server to local files due to security reasons. However you can open the browser in allowed access mode. Just open the terminal and go to the folder where chrome.exe is stored and write the following command.
chrome.exe --allow-file-access-from-files
Read this for more details
This way, However, didn't work for me so I made a different route for every file in a particular directory. Therefore, going to that path meant opening that file.
function getroutes(list){
list.forEach(function(element) {
app.get("/"+ element, function(req, res) {
res.sendFile(__dirname + "/public/extracted/" + element);
});
});
}
I called this function passing the list of filename in the directory __dirname/public/extracted and it created a different route for each filename which I was able to render on server side.
This is for google-chrome-extension
const url = "file:///C:\002.jpg"
chrome.tabs.create({url, active:true})
manifest.json
{
"name": "",
"manifest_version": 3,
"permissions": [
"activeTab",
"tabs"
],
// ...
}
This solution worked for me in PHP. It opens the PDF in the browser.
// $path is the path to the pdf file
public function showPDF($path) {
if($path) {
header("Content-type: application/pdf");
header("Content-Disposition: inline; filename=filename.pdf");
#readfile($path);
}
}
I've encounterd this problem, and here is my solution for Angular, I wrapped my Angular's asset folder in encodeURIComponent() function. It worked. But still, I'd like to know more about the risk of this solution if there's any:
```const URL = ${encodeURIComponent(/assets/office/file_2.pdf)}
window.open(URL)
I used Angular 9, so this is my url when I clicked open local file:
```http://localhost:4200/%2Fassets%2Foffice%2Ffile_2.pdf```
In the case of audio files, when you give <audio src="C://somePath"/>, this throws an error saying cannot load local resource.
This makes sense because any webpage can't simply give a local path and access your private files.
In case you are trying to play audio with dynamic paths, by changing src property through JS, then here is a sample implementation using Flask server and HTML.
server.py
#app.route("/")
def home():
return render_template('audioMap.html')
#app.route('/<audio_file_name>')
def view_method(audio_file_name):
path_to_audio_file = "C:/Audios/yourFolderPath" + audio_file_name
return send_file(
path_to_audio_file,
mimetype="audio/mp3",
as_attachment=True,
attachment_filename="test.mp3")
audioMap.html
{% raw %}
<!DOCTYPE html>
<html>
<body>
AUDIO: <audio src="Std.mp3" controls >
</body>
</html>
{% endraw %}
Explanation:
When you give the audio file name under src property, this creates a get request in the flask as shown
127.0.0.1 - - [04/May/2021 21:33:12] "GET /Std.mp3 HTTP/1.1" 200 -
As you can see that, the flask has sent a Get request for the Std.mp3 file. So to serve this get request, we wrote an endpoint that takes the audio file name, reads it from the local directory, and returns it back. Hence the audio shows up on UI.
Note: This works only if you are rendering your HTML file using the
render_template method via flask or to say, using flask as your web server.
Google Chrome does not allow to load local resources because of the security .
There is a simple solution for this problem .
1.install live-server plugin in vscode
2.open the html file by live-server

Embedding external link inside Electron

I've got an array of instagram media data prepared for embedding. In the end of each html there's a script <script async defer src="//platform.instagram.com/en_US/embeds.js"></script>.
By default electron refers this link to the file:// protocol. Adding http:// in src return js file correctly.
So link <script async defer src="http://platform.instagram.com/en_US/embeds.js"></script> works fine.
How can I solve this problem except parsing data and rewriting link?
The problem you are facing is that // is a protocol relative URL that will use whatever protocol the file requesting it is. You can read more about that here.
your best bet to override this default behaviour would be to either parse the data and rewrite the links with something like a regex query.
or you can attempt to intercept the file protocol, verify that the url is one you want to intercept, then reformat the url, you can learn about how to do this here. with an example that does not include the verification of the paths you wish to intercept below.
const {app, protocol} = require('electron')
const path = require('path')
app.on('ready', () => {
protocol.registerFileProtocol('file', (request, callback) => {
const url = request.url.substr(7)
callback({path: path.normalize(`http://${__dirname}/${url}`)})
}, (error) => {
if (error) console.error('Failed to register protocol')
})
})

How to stream video data to a video element?

I have a Node.js process which outputs a video stream into my Node.js app.
On the client end, there is a <video> tag. I would like to stream the video from Node.js into the src attribute of the video tag. My previous experience tells me that we must use the blob object for this. However, I'm not a hundred percent certain how and why I would use it.
Another possible solution I'm thinking of is to create some sort of a temporary file on my server, then write the stream to that file, then serve that file as the source for the video. However, that doesn't seem intuitive. I was wondering, then, if there is a more established solution for an issue like this.
m3u8 format is commonly used for streaming.
Video streaming/transcoding is a resource intensive thing. I would suggest you to use third party service to do so, if you have that option.
Probably you might want to look at the following options:
BinaryJS. It's bidrectional realtime binary data transfer tool based on websockets.
JSMpeg stream-server (in case of capturing) from Phoboslab guys. All you need to do is start ffmpeg and point it to the domain and port where the nodejs script is running.
More info you can find here.
Pipe a stream directly. Good answer is posted here. In few words you just need to specify Accept-Ranges, Content-Range, Content-Length and Content-Type headers, then create relevant Read stream (with start and end options) and pipe it to the response object.
I've actually tried this at a hackathon two weeks ago. I ended up barely getting this flv stream to work, which I've posted below. My intent was to make a library to automate much of the processes this would entail.
As you can see, I've opened a new port on the server to handle the separate stream of data flowing to the client. This is reflected in the client's src tag.
THREE THINGS YOU NEED:
This Linux version of ffmpeg.
Flowplayer on the js side.
npm fluent-ffmpeg
// StreamServer.js
var express = require('express'),
app = express(),
ffmpeg = require('fluent-ffmpeg');
module.exports = function () {
app.stream(req, res)
{
res.contentType('flv');
// make sure you set the correct path to your video file storage
var pathToMovie = '/path/to/storage/' + req.params.filename;
var proc = ffmpeg(pathToMovie)
// use the 'flashvideo' preset (located in /lib/presets/flashvideo.js)
.preset('flashvideo')
// setup event handlers
.on('end', function () {
console.log('file has been converted succesfully');
})
.on('error', function (err) {
console.log('an error happened: ' + err.message);
})
// save to stream
.pipe(res, { end: true });
};
}
//routes.js
'use strict';
var stream = require('../controllers/streaming.server.controller'),
streamServer = require('../controllers/StreamServer.js'),
express = require('express');
//streaming.server.controller.js
module.exports = function (app) {
app.get('/api/stream', function (req, res) {
streamServer.stream(req, res);
});
};
var path = require('path'),
express = require('express'),
app = express(),
routes = require('../routes/routes.js')(app),
ffmpeg = require('fluent-ffmpeg');
app.listen(4000);
EDIT: Client side part:
https://github.com/fluent-ffmpeg/node-fluent-ffmpeg/tree/master/examples/flowplayer
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<script type="text/javascript" src="/flowplayer.min.js"></script>
<title>node-fluent-ffmpeg</title>
</head>
<body>
<!-- this A tag is where your Flowplayer will be placed. it can be anywhere -->
<a
href="http://localhost:4000/api/stream"
style="display:block;width:520px;height:330px"
id="player">
</a>
<!-- this will install flowplayer inside previous A- tag. -->
<script>
flowplayer("player", "/flowplayer.swf");
</script>
</body>
</html>
(Just change the href attribute)

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