Chrome extension, file from string? - javascript

I'm building chrome extension for watching videos.
I have problem with adding subtitles and captions to video. I have subtitle as string (from ajax call), and problem is that <track> tag in html5 requires a file, (url to file).
Is there a good way to create a file from string in chrome exstension / javascript, and than accessing it via url/path?
Thx

Creating an URL from a string is very easy with the Blob constructor and URL.createObjectURL:
var content = 'some string';
var url = URL.createObjectURL(new Blob([content], { type: 'text/plain' }));
If you're using AJAX, then you don't need to do a string-to-blob conversion. Just set responseType = 'blob'; directly:
var x = new XMLHttpRequest();
x.open('GET', 'http://example.com/');
x.responseType = 'blob';
x.onload = function() {
var url = URL.createObjectURL(x.response);
// ...
};
x.send();

Instead of creating a file, you can try generating a data URI:
src = 'data:text/plain,' + encodeURIComponent(subtitleString);
or:
src = 'data:text/plain;base64,' + btoa(subtitleString);
You'll need to add encoding info if you are dealing with non US-ASCII subtitles.

Related

How to download an image with Python 3/Selenium if the URL begins with "blob:"?

When using web.whatsapp.de one can see that the link to a recieved image may look like this:
blob:https://web.whatsapp.com/3565e574-b363-4aca-85cd-2d84aa715c39
If the link is copied in to an address window it will open up the image, however - if "blob" is left out - it will simply open a new web whatsapp window.
I am trying to download the image displayed by this link.
But using common techniques such as using request, or urllib.request or even BeautifulSoup always struggle at one point: The "blob" at the beginning of the url will throw an error.
These answers Download file from Blob URL with Python will trhow either the Error
URLError: <urlopen error unknown url type: blob>
or the Error
InvalidSchema: No connection adapters were found for 'blob:https://web.whatsapp.com/f50eac63-6a7f-48a4-a2b8-8558a9ffe015'
(using BeatufilSoup)
Using a native approach like:
import requests
url = 'https://web.whatsapp.com/f50eac63-6a7f-48a4-a2b8-8558a9ffe015'
fileName = 'test.png'
req = requests.get(url)
file = open(fileName, 'wb')
for chunk in req.iter_content(100000):
file.write(chunk)
file.close()
Will simply result in the same error as using BeautifulSoup.
I am controlling Chrome using Selenium in Python, however I was unable to download the image correctly using the provided link.
A blob is a filelike object of raw data stored by the browser.
You can see them at chrome://blob-internals/
It's possible to get the content of a blob with Selenium with a script injection. However, you'll have to comply to the cross origin policy by running the script on the page/domain that created the blob:
def get_file_content_chrome(driver, uri):
result = driver.execute_async_script("""
var uri = arguments[0];
var callback = arguments[1];
var toBase64 = function(buffer){for(var r,n=new Uint8Array(buffer),t=n.length,a=new Uint8Array(4*Math.ceil(t/3)),i=new Uint8Array(64),o=0,c=0;64>c;++c)i[c]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".charCodeAt(c);for(c=0;t-t%3>c;c+=3,o+=4)r=n[c]<<16|n[c+1]<<8|n[c+2],a[o]=i[r>>18],a[o+1]=i[r>>12&63],a[o+2]=i[r>>6&63],a[o+3]=i[63&r];return t%3===1?(r=n[t-1],a[o]=i[r>>2],a[o+1]=i[r<<4&63],a[o+2]=61,a[o+3]=61):t%3===2&&(r=(n[t-2]<<8)+n[t-1],a[o]=i[r>>10],a[o+1]=i[r>>4&63],a[o+2]=i[r<<2&63],a[o+3]=61),new TextDecoder("ascii").decode(a)};
var xhr = new XMLHttpRequest();
xhr.responseType = 'arraybuffer';
xhr.onload = function(){ callback(toBase64(xhr.response)) };
xhr.onerror = function(){ callback(xhr.status) };
xhr.open('GET', uri);
xhr.send();
""", uri)
if type(result) == int :
raise Exception("Request failed with status %s" % result)
return base64.b64decode(result)
bytes = get_file_content_chrome(driver, "blob:https://developer.mozilla.org/7f9557f4-d8c8-4353-9752-5a49e85058f5")
Blobs are not actual files to be remotely retrieved by a URI. Instead, they are programatically generated psuedo-URLs which are mapped to binary data in order to give the browser something to reference. I.e. there is no attribute of <img> to provide raw data so you instead create a blob address to map that data to the standard src attribute.
From the MDN page linked above:
The only way to read content from a Blob is to use a FileReader. The following code reads the content of a Blob as a typed array.
var reader = new FileReader();
reader.addEventListener("loadend", function() {
// reader.result contains the contents of blob as a typed array
});
reader.readAsArrayBuffer(blob);
For people who are trying to do the same in node and selenium, please refer below.
var script = function (blobUrl) {
console.log(arguments);
var uri = arguments[0];
var callback = arguments[arguments.length - 1];
var toBase64 = function(buffer) {
for(var r,n=new Uint8Array(buffer),t=n.length,a=new Uint8Array(4*Math.ceil(t/3)),i=new Uint8Array(64),o=0,c=0;64>c;++c)
i[c]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".charCodeAt(c);for(c=0;t-t%3>c;c+=3,o+=4)r=n[c]<<16|n[c+1]<<8|n[c+2],a[o]=i[r>>18],a[o+1]=i[r>>12&63],a[o+2]=i[r>>6&63],a[o+3]=i[63&r];return t%3===1?(r=n[t-1],a[o]=i[r>>2],a[o+1]=i[r<<4&63],a[o+2]=61,a[o+3]=61):t%3===2&&(r=(n[t-2]<<8)+n[t-1],a[o]=i[r>>10],a[o+1]=i[r>>4&63],a[o+2]=i[r<<2&63],a[o+3]=61),new TextDecoder("ascii").decode(a)
};
var xhr = new XMLHttpRequest();
xhr.responseType = 'arraybuffer';
xhr.onload = function(){ callback(toBase64(xhr.response)) };
xhr.onerror = function(){ callback(xhr.status) };
xhr.open('GET', uri);
xhr.send();
}
driver.executeAsyncScript(script, imgEleSrc).then((result) => {
console.log(result);
})
For detailed explanation, please refer below link
https://medium.com/#anoop.goudar/how-to-get-data-from-blob-url-to-node-js-server-using-selenium-88b1ad57e36d

Display embedded PDF in Internet Explorer 11 from binary string or base64

There is a 3rd party service which sends me a PDF file in either binary string or base64 encoded. Is there any possibility to display the PDF embedded in IE 11 using either binary string or base64 encoded.
From SO and other forums, I concluded that IE 11 supports data uri only for images and not PDF (I might be wrong) which rules out base64. So the only option left is to display from binary string. I am using it in a Node App but I do not have the option to first save the retrieved file to Node server and use static URL.
Please let me know if above is achievable in IE 11.
Currently I'm trying to use npm package of https://github.com/pipwerks/PDFObject. For Chrome & Firefox, I retrieve the base64 file and embed it using the above package and works fine.
This solution uses [pdf.js] 1
Key steps in rendering a base64 PDF using PDF.js library
First decode it using atob
Then initializing a Uint8Array using above decoded data
Abstract from express-pdfjs/scripts/App.js
let options = {
method: 'GET',
uri: 'http://localhost:5000/getBase64Pdf',
resolveWithFullResponse: true
}
rp(options)
.then((response) => {
if (response.statusCode !== 200) {
console.error('http not 200 but : ', response.statusCode)
} else {
console.info('connected successfully : ' + response.statusCode)
let pdfData = atob(response.body)
let uint8ArrayPdf = new Uint8Array(pdfData.length)
for (let i = 0; i < pdfData.length; i++) {
uint8ArrayPdf[i] = pdfData.charCodeAt(i)
}
let pdfjsframe = document.getElementById('pdfViewer');
pdfjsframe.contentWindow.PDFViewerApplication.open(uint8ArrayPdf);
}
})
pdfViewer is an iframe in index.html
<iframe id="pdfViewer" src="http://localhost:3000/express-pdfjs/pdfViewer/web/viewer.html" height="1600" width="850" />
Please find a sample implementation for this using React on client
side
# https://github.com/rohanray/so-pdf-base64
Following the discussion with #roray - I'm adding a slightly different solution on the menu here :)
First off: 1.not using base64 string for this (although possible). 2. I'm working on asp mvc 3. using viewer.html viewer of pdf.js
So, from the server/controller fetch file from db and return bites
public ActionResult LoadFile(int id)
{
var file = db.Files.Where(i => i.Id == id).FirstOrDefault();
return File(file.BinaryFile, MediaTypeNames.Application.Pdf, "Name.pdf");
}
In the view/html add an iframe with source unspecified (src="") alternatively can created it on the fly on page-load event.BTW, I tried object, embed and iframe with FF/Chrome/Edge/IE 11 and found iframe seems to work consistently across the board. Dont like iframe though :/
<iframe src="" name="printDoc" id="printDoc" width="800" height="1000" type="application/pdf"></iframe>
Finally, in your script tag. This can be done via Ajax just the same. Basically, soon as the document is ready call the server, get the file in bytes, convert to blob url, append the blob url to the relative location of '/web/viewer.html?file=' in your project and update the src="" attribute of your iframe.
$(document).ready(function myfunction() {
var xhr = new XMLHttpRequest();
// works for EDGE/Chrome/FFox
xhr.open("GET", "/Documents/LoadFile/" + fileId, true);
xhr.responseType = "blob";
xhr.onload = function (e) {
if (this.status === 200) {
var blob = new Blob([this.response], { type: 'application/pdf' });
console.log('Not IE 11');
var url = window.URL.createObjectURL(blob);
_iFrame = document.querySelector("#printDoc");
_iFrame.setAttribute('src', '/web/viewer.html?file=' + url);
}
};
xhr.send();
});
This will open the pdf embedded in the viewer.html embedded in the iframe. MS Edge works fine with this but not the blob url being sent as a query param over the address bar which obviously is supported by FF/Chrome. And, that's why I took this option.
PS. IE 11 remains hopeless for me so I used var blob = new Blob([this.response], {type: 'application/pdf' });window.navigator.msSaveOrOpenBlob(blob, fileName);Please let me know if you find a way to improve IE 11 performance

Using raw image data from ajax request for data URI

I'm trying to use a combination of Ajax and data URIs to load a JPEG image and extract its EXIF data with a single HTTP request. I am modifying a library (https://github.com/kennydude/photosphere) to do this; currently this library uses two HTTP requests to set the source of the image and to get the EXIF data.
Getting the EXIF works, no problem. However I am having difficulty using the raw data from the ajax request as source for the image.
Source code for a small test of the technique:
<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'>
function init()
{
// own ajax library - using it to request a test jpg image
new Ajax().sendRequest
(
"/images/photos/badger.jpg",
{ method : "GET",
callback: function(xmlHTTP)
{
var encoded = btoa (unescape(encodeURIComponent(xmlHTTP.responseText)));
var dataURL="data:image/jpeg;base64,"+encoded;
document.getElementById("image").src = dataURL;
}
}
);
}
</script>
<script type="text/javascript" src="http://www.free-map.org.uk/0.6/js/lib/Ajax.js"></script>
</head>
<body onload='init()'>
<img id="image" alt="data url loaded image" />
</body>
</html>
I get what looks like sensible jpeg data sent back, and the length (in bytes) of the raw data and the base64-encoded-then-unencoded-again raw data is the same. However the attempt to set the image src fails on both Firefox (25) and Chrome (31) (current versions) - chrome displays "broken image" icon suggesting the src is an invalid format.
I used this mozilla page for info on base64 encoding/decoding:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Base64_encoding_and_decoding
Any idea what might be wrong? Looking around I can create the base64 encoded image server side but can it be done client side like this? For one thing, base64 encoding server side obviously increases the data size and the whole purpose of this exercise is to cut down the amount of data being transferred from the server, as well as the number of requests.
Thanks,
Nick
Thanks for that. I've done a bit more digging on this and it turns out there is a solution at least on current versions of Firefox and Chrome (EDIT: IE10 works too). You can use XMLHttpRequest2 and use a typed array (Uint8Array). The following code works:
<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'>
function init()
{
var xmlHTTP = new XMLHttpRequest();
xmlHTTP.open('GET','/images/photos/badger.jpg',true);
// Must include this line - specifies the response type we want
xmlHTTP.responseType = 'arraybuffer';
xmlHTTP.onload = function(e)
{
var arr = new Uint8Array(this.response);
// Convert the int array to a binary string
// We have to use apply() as we are converting an *array*
// and String.fromCharCode() takes one or more single values, not
// an array.
var raw = String.fromCharCode.apply(null,arr);
// This works!!!
var b64=btoa(raw);
var dataURL="data:image/jpeg;base64,"+b64;
document.getElementById("image").src = dataURL;
};
xmlHTTP.send();
}
</script>
</head>
<body onload='init()'>
<img id="image" alt="data url loaded image" />
</body>
</html>
Basically you ask for a binary response, then create an 8-bit unsigned int view of the data before converting it back into a (binary-friendly) string String.fromCharCode(). The apply is necessary as String.fromCharCode() does not accept an array argument. You then use btoa(), create your data url and it then works.
The following resources were useful for this:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays?redirectlocale=en-US&redirectslug=JavaScript%2FTyped_arrays
and
http://www.html5rocks.com/en/tutorials/file/xhr2/
Nick
Nick's answer works very well. But when I did this with a fairly large file, I got a stack overflow on
var raw = String.fromCharCode.apply(null,arr);
Generating the raw string in chunks worked well for me.
var raw = '';
var i,j,subArray,chunk = 5000;
for (i=0,j=arr.length; i<j; i+=chunk) {
subArray = arr.subarray(i,i+chunk);
raw += String.fromCharCode.apply(null, subArray);
}
I had trouble with the ArrayBuffer -> String -> Base64 method described above, but ran across another method using Blob that worked great. It's not a way to convert raw data to Base 64 (as in the title), but it is a way to display raw image data (as in the actual question):
var xhr = new XMLHttpRequest();
xhr.responseType = 'arraybuffer';
xhr.onload = function() {
var blb = new Blob([xhr.response], {type: 'image/png'});
var url = (window.URL || window.webkitURL).createObjectURL(blb);
image.src = url;
}
xhr.open('GET', 'http://whatever.com/wherever');
xhr.send();
All credit goes to Jan Miksovsky, author of this fiddle. I just stumbled across it and thought it'd make a useful addition to this discussion.
Modern ES6 powered solution for image downloading: (without specifying image type)
async function downloadImageFromUrl(url) { // returns dataURL
const xmlHTTP = new XMLHttpRequest();
xmlHTTP.open('GET', url, true);
xmlHTTP.responseType = 'blob';
const imageBlob = await new Promise((resolve, reject) => {
xmlHTTP.onload = e => xmlHTTP.status >= 200 && xmlHTTP.status < 300 && xmlHTTP.response.type.startsWith('image/') ? resolve(xmlHTTP.response) : reject(Error(`wrong status or type: ${xmlHTTP.status}/${xmlHTTP.response.type}`));
xmlHTTP.onerror = reject;
xmlHTTP.send();
});
return blobToDataUrl(imageBlob);
}
function blobToDataUrl(blob) { return new Promise(resolve => {
const reader = new FileReader(); // https://developer.mozilla.org/en-US/docs/Using_files_from_web_applications
reader.onload = e => resolve(e.target.result);
reader.readAsDataURL(blob);
})}
Usage:
downloadImageFromUrl('https://a.b/img.png').then(console.log, console.error)
I've been working for two days on this issue since I needed a solution to render the User's Outlook Profile Picture from the raw data received from Microsoft Graft. I have implemented all the solutions above, with no success. Then I found this git:
get base64 raw data of image from responseBody using jquery ajax
In my case, I just replaced "data:image/png;base64," with "data:image/jpg;base64,"
It works like a charm.
You will have to do base64 encoding on the server side as the responseText is treated as a String, and the response data that the server is sending is binary.

How to give a Blob uploaded as FormData a file name?

I am currently uploading images pasted from the clipboard with the following code:
// Turns out getAsFile will return a blob, not a file
var blob = event.clipboardData.items[0].getAsFile(),
form = new FormData(),
request = new XMLHttpRequest();
form.append("blob",blob);
request.open(
"POST",
"/upload",
true
);
request.send(form);
Turns out the uploaded form field with receive a name similar to this: Blob157fce71535b4f93ba92ac6053d81e3a
Is there any way to set this or receive this file name client side, without doing any server side communication?
For Chrome, Safari and Firefox, just use this:
form.append("blob", blob, filename);
(see MDN documentation)
Adding this here as it doesn't seem to be here.
Aside from the excellent solution of form.append("blob",blob, filename); you can also turn the blob into a File instance:
var blob = new Blob([JSON.stringify([0,1,2])], {type : 'application/json'});
var fileOfBlob = new File([blob], 'aFileName.json');
form.append("upload", fileOfBlob);
Since you're getting the data pasted to clipboard, there is no reliable way of knowing the origin of the file and its properties (including name).
Your best bet is to come up with a file naming scheme of your own and send along with the blob.
form.append("filename",getFileName());
form.append("blob",blob);
function getFileName() {
// logic to generate file names
}
That name looks derived from an object URL GUID. Do the following to get the object URL that the name was derived from.
var URL = self.URL || self.webkitURL || self;
var object_url = URL.createObjectURL(blob);
URL.revokeObjectURL(object_url);
object_url will be formatted as blob:{origin}{GUID} in Google Chrome and moz-filedata:{GUID} in Firefox. An origin is the protocol+host+non-standard port for the protocol. For example, blob:http://stackoverflow.com/e7bc644d-d174-4d5e-b85d-beeb89c17743 or blob:http://[::1]:123/15111656-e46c-411d-a697-a09d23ec9a99. You probably want to extract the GUID and strip any dashes.
Haven't tested it, but that should alert the blobs data url:
var blob = event.clipboardData.items[0].getAsFile(),
form = new FormData(),
request = new XMLHttpRequest();
var reader = new FileReader();
reader.onload = function(event) {
alert(event.target.result); // <-- data url
};
reader.readAsDataURL(blob);
It really depends on how the server on the other side is configured and with what modules for how it handles a blob post. You can try putting the desired name in the path for your post.
request.open(
"POST",
"/upload/myname.bmp",
true
);
Are you using Google App Engine?
You could use cookies (made with JavaScript) to maintain a relationship between filenames and the name received from the server.
When you are using Google Chrome you can use/abuse the Google Filesystem API for this. Here you can create a file with a specified name and write the content of a blob to it. Then you can return the result to the user.
I have not found a good way for Firefox yet; probably a small piece of Flash like downloadify is required to name a blob.
IE10 has a msSaveBlob() function in the BlobBuilder.
Maybe this is more for downloading a blob, but it is related.

Ajax Binary Response

Hi I'm wondering if there's anyway to stream a binary response in AJAX? This would be an ultimate solution otherwise I would need to realize the binary image to a file then stream that file to the user with a different URL.
new Ajax.Request('/viewImage?id=123', {
// request returns a binary image inputstream
onSuccess: function(transport) {
// text example
// alert(transport.responseText)
// QUESTION: is there a streaming binary response?
$('imgElem').src = transport.responseBinary;
},
onFailure: function(transport) {
// handle failure
}
});
It might not be possible to stream binary data, but you can use Ajax to retrieve binary data.
This is possible using one of two methods: Javascript Typed Arrays or an XMLHttpResponse overrideMimeType hack. Have a read of a good article on MDN – these examples are taken from there: Sending and Receiving Binary Data
The Typed Array method looks like this:
var oReq = new XMLHttpRequest();
oReq.open("GET", "/myfile.png", true);
oReq.responseType = "arraybuffer";
oReq.onload = function (oEvent) {
var arrayBuffer = oReq.response; // Note: not oReq.responseText
if (arrayBuffer) {
var byteArray = new Uint8Array(arrayBuffer);
for (var i = 0; i < byteArray.byteLength; i++) {
// do something with each byte in the array
}
}
};
oReq.send(null);
Typed Arrays are not supported in IE < 10, Firefox < 4, Chrome < 7, Safari < 5.1 and Opera < 11.6, and mobile support is shaky but improving.
The second method uses an XMLHttpRequest method called overrideMimeType to allow the binary data to be passed through unmodified.
var req = new XMLHttpRequest();
req.open('GET', '/myfile.png', false);
// XHR binary charset opt by Marcus Granado 2006 [http://mgran.blogspot.com]
req.overrideMimeType('text\/plain; charset=x-user-defined');
req.send(null);
if (req.status != 200) return '';
// do stuff with req.responseText;
You get an unparsed binary string, upon which you can use var byte = filestream.charCodeAt(x) & 0xff; to retrieve a specific byte.
This is an extension to Tom Ashworth's response (which helped to put me on the right track with the issue I was facing). This allows you to just get the filestream (FileStreamResult if you are using asp.net mvc) and set it to the img src, which is cool.
var oReq = new XMLHttpRequest();
oReq.open("post", '/somelocation/getmypic', true );
oReq.responseType = "blob";
oReq.onload = function ( oEvent )
{
var blob = oReq.response;
var imgSrc = URL.createObjectURL( blob );
var $img = $( '<img/>', {
"alt": "test image",
"src": imgSrc
} ).appendTo( $( '#bb_theImageContainer' ) );
window.URL.revokeObjectURL( imgSrc );
};
oReq.send( null );
The basic idea is that the data is returned untampered with, it is placed in a blob and then a url is created to that object in memory. See here and here. Note supported browsers.
What you can do, if you are trying to generate an image on the fly, is to just do:
<img src="http://myurl/myfile.php?id=3" />
then you can send the data with the appropriate mimetype.
If you really want to send an image, then you may want to look at the HTML5 canvas tag, but I am not certain how excanvas would work with this, for being cross-platform.
You could write to the canvas, but it would be more efficient to just use the img tag.
When you call your service, you should ask for a dataType: 'binary' response. Then, you can use saveAs(FileSaver.js) to trigger the download or createObjectURL to open in new window.
But, $.ajax doesn't let you download binary content out of the box, it will try to decode your binary from UTF-8 and corrupt it. Either use a jQuery plugin to solve this problem jquery.binarytransport.js
exemplo:
$.ajax({
type: "POST",
url: $("form#data").attr("action"),
data: formData,
dataType: 'binary', //--> using jquery.binarytransport.js
success: function (response) {
// Default response type is blob
saveAs(response, "test.pdf"); //--> using FileSaver.js
let fileURL = URL.createObjectURL(blob);
window.open(fileURL); // open file in new window
}
});
Good look! :)
You can send any response you want, being it plain text, HTML, an image... whatever! It's up to you how to handle it when you receive it.
But... you cannot assign a binary image to the <IMG> src attribute. You'd better just return the URL to the image and assign that instead - well, to be honest, there are some encodings to embed images in the SRC, but they are not cross-browser so you'll want to stay away from them.
I managed to get download of binary file without corrupted data working using jQuery ajax by adding:
xhrFields: {responseType: 'blob'}

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