I'm using Dropzone to do a image check and tell the user if the resolution is good enough for production.
When files are in RAW format (dng, cr2, orf, etc), I want them to be automatically APPROVED (as if they where uploaded) but WITHOUT actually uploading them (RAW files are large and would take too long to upload).
Basically what I mean is that the file would stay in the list with a check-mark but would not be sent to php. Is this possible?
Currently I'm trying to refuse those files based on their type and then programmatically change them to "success". But I can't seem to find how.
var counter = 0;
myDropzone.on("sending", function(file) {
if(file.type == "image/cr2"){
myDropzone.files[counter].accepted = false;
}
counter++;
});
I don't think dropzone is going to identify the file type of those formats, but you can check if the filename contains the extension you want, here an example:
var formats = ['.orf', '.cr2', '.dng'];
Dropzone.autoDiscover = false;
var myDropzone = $('#yourDropzoneId').dropzone({
accept: function (file, done) {
var extension = '.' + file.name.toLowerCase().split('.').slice(-1)[0];
if (formats.indexOf(extension) >= 0) {
done('OK');
$('.dz-preview').last().toggleClass('dz-error dz-success');
}
else {
done();
}
}
});
In this example the files with a extension specified in the array will be rejected but then is going to simulate a success, the other files with a different extension will be uploaded.
A Little Background
I've been working for a couple of days on a Chrome extension that takes a screenshot of given web pages multiple times a day. I used this as a guide and things work as expected.
There's one minor requirement extensions can't meet, though. The user must have access to the folder where the images (screenshots) are saved but Chrome Extensions don't have access to the file system. Chrome Apps, on the other hand, do. Thus, after much looking around, I've concluded that I must create both a Chrome Extension and a Chrome App. The idea is that the extension would create a blob of the screenshot and then send that blob to the app which would then save it as an image to a user-specified location. And that's exactly what I'm doing — I'm creating a blob of the screentshot on the extension side and then sending it over to the app where the user is asked to choose where to save the image.
The Problem
Up to the saving part, everything works as expected. The blob is created on the extension, sent over to the app, received by the app, the user is asked where to save, and the image is saved.... THAT is where things fall apart. The resulting image is unusable. When I try to open it, I get a message that says "Can't determine type". Below is the code I'm using:
First ON THE EXTENSION side, I create a blob and send it over, like this:
chrome.runtime.sendMessage(
APP_ID, /* I got this from the app */
{myMessage: blob}, /* Blob created previously; it's correct */
function(response) {
appendLog("response: "+JSON.stringify(response));
}
);
Then, ON THE APP side, I receive the blob and attempt to save it like this:
// listen for external messages
chrome.runtime.onMessageExternal.addListener(
function(request, sender, sendResponse) {
if (sender.id in blacklistedIds) {
sendResponse({"result":"sorry, could not process your message"});
return; // don't allow this extension access
} else if (request.incomingBlob) {
appendLog("from "+sender.id+": " + request.incomingBlob);
// attempt to save blob to choosen location
if (_folderEntry == null) {
// get a directory to save in if not yet chosen
openDirectory();
}
saveBlobToFile(request.incomingBlob, "screenshot.png");
/*
// inspect object to try to see what's wrong
var keys = Object.keys(request.incomingBlob);
var keyString = "";
for (var key in keys) {
keyString += " " + key;
}
appendLog("Blob object keys:" + keyString);
*/
sendResponse({"result":"Ok, got your message"});
} else {
sendResponse({"result":"Ops, I don't understand this message"});
}
}
);
Here's the function ON THE APP that performs the actual save:
function saveBlobToFile(blob, fileName) {
appendLog('entering saveBlobToFile function...');
chrome.fileSystem.getWritableEntry(_folderEntry, function(entry) {
entry.getFile(fileName, {create: true}, function(entry) {
entry.createWriter(function(writer) {
//writer.onwrite = function() {
// writer.onwrite = null;
// writer.truncate(writer.position);
//};
appendLog('calling writer.write...');
writer.write(blob);
// Also tried writer.write(new Blob([blob], {type: 'image/png'}));
});
});
});
}
There are no errors. No hiccups. The code works but the image is useless. What exactly am I missing? Where am I going wrong? Is it that we can only pass strings between extensions/apps? Is the blob getting corrupted on the way? Does my app not have access to the blob because it was created on the extension? Can anyone please shed some light?
UPDATE (9/23/14)
Sorry for the late update, but I was assigned to a different project and could not get back to this until 2 days ago.
So after much looking around, I've decided to go with #Danniel Herr's suggestion which suggests to use a SharedWorker and a page embedded in a frame in the app. The idea is that the Extension would supply the blob to the SharedWorker, which forwards the blob to a page in the extension that is embedded in a frame in the app. That page, then forwards the blob to the app using parent.postMessage(...). It's a bit cumbersome but it seems it's the only option I have.
Let me post some code so that it makes a bit more sense:
Extension:
var worker = new SharedWorker(chrome.runtime.getURL('shared-worker.js'));
worker.port.start();
worker.postMessage('hello from extension'); // Can send blob here too
worker.port.addEventListener("message", function(event) {
$('h1Title').innerHTML = event.data;
});
proxy.js
var worker = new SharedWorker(chrome.runtime.getURL('shared-worker.js'));
worker.port.start();
worker.port.addEventListener("message",
function(event) {
parent.postMessage(event.data, 'chrome-extension://[extension id]');
}
);
proxy.html
<script src='proxy.js'></script>
shared-worker.js
var ports = [];
var count = 0;
onconnect = function(event) {
count++;
var port = event.ports[0];
ports.push(port);
port.start();
/*
On both the extension and the app, I get count = 1 and ports.length = 1
I'm running them side by side. This is so maddening!!!
What am I missing?
*/
var msg = 'Hi, you are connection #' + count + ". ";
msg += " There are " + ports.length + " ports open so far."
port.postMessage(msg);
port.addEventListener("message",
function(event) {
for (var i = 0; i < ports.length; ++i) {
//if (ports[i] != port) {
ports[i].postMessage(event.data);
//}
}
});
};
On the app
context.addEventListener("message",
function(event) {
appendLog("message from proxy: " + event.data);
}
);
So this is the execution flow... On the extension I create a shared worker and send a message to it. The shared worker should be capable of receiving a blob but for testing purposes I'm only sending a simple string.
Next, the shared worker receives the message and forwards it to everyone who has connected. The proxy.html/js which is inside a frame in the app has indeed connected at this point and should receive anything forwarded by the shared worker.
Next, proxy.js [should] receives the message from the shared worker and sends it to the app using parent.postMessage(...). The app is listening via a window.addEventListener("message",...).
To test this flow, I first open the app, then I click the extension button. I get no message on the app. I get no errors either.
The extension can communicate back and forth with the shared worker just fine. The app can communicate with the shared worker just fine. However, the message I sent from the extension->proxy->app does not reach the app. What am I missing?
Sorry for the long post guys, but I'm hoping someone will shed some light as this is driving me insane.
Thanks
Thanks for all your help guys. I found the solution to be to convert the blob into a binary string on the extension and then send the string over to the app using chrome's message passing API. On the app, I then did what Francois suggested to convert the binary string back a blob. I had tried this solution before but I had not worked because I was using the following code on the app:
blob = new Blob([blobAsBinString], {type: mimeType});
That code may work for text files or simple strings, but it fails for images (perhaps due to character encoding issues). That's where I was going insane. The solution is to use what Francois provided since the beginning:
var bytes = new Uint8Array(blobAsBinString.length);
for (var i=0; i<bytes.length; i++) {
bytes[i] = blobAsBinString.charCodeAt(i);
}
blob = new Blob([bytes], {type: mimeString});
That code retrains the integrity of the binary string and the blob is recreated properly on the app.
Now I also incorporated something I found suggested by some of you here and RobW elsewhere, which is to split the blob into chunks and send it over like that, in case the blob is too large. The entire solution is below:
ON THE EXTENSION:
function sendBlobToApp() {
// read the blob in chunks/chunks and send it to the app
// Note: I crashed the app using 1 KB chunks. 1 MB chunks work just fine.
// I decided to use 256 KB as that seems neither too big nor too small
var CHUNK_SIZE = 256 * 1024;
var start = 0;
var stop = CHUNK_SIZE;
var remainder = blob.size % CHUNK_SIZE;
var chunks = Math.floor(blob.size / CHUNK_SIZE);
var chunkIndex = 0;
if (remainder != 0) chunks = chunks + 1;
var fr = new FileReader();
fr.onload = function() {
var message = {
blobAsText: fr.result,
mimeString: mimeString,
chunks: chunks
};
// APP_ID was obtained elsewhere
chrome.runtime.sendMessage(APP_ID, message, function(result) {
if (chrome.runtime.lastError) {
// Handle error, e.g. app not installed
// appendLog is defined elsewhere
appendLog("could not send message to app");
}
});
// read the next chunk of bytes
processChunk();
};
fr.onerror = function() { appendLog("An error ocurred while reading file"); };
processChunk();
function processChunk() {
chunkIndex++;
// exit if there are no more chunks
if (chunkIndex > chunks) {
return;
}
if (chunkIndex == chunks && remainder != 0) {
stop = start + remainder;
}
var blobChunk = blob.slice(start, stop);
// prepare for next chunk
start = stop;
stop = stop + CHUNK_SIZE;
// convert chunk as binary string
fr.readAsBinaryString(blobChunk);
}
}
ON THE APP
chrome.runtime.onMessageExternal.addListener(
function(request, sender, sendResponse) {
if (sender.id in blacklistedIds) {
return; // don't allow this extension access
} else if (request.blobAsText) {
//new chunk received
_chunkIndex++;
var bytes = new Uint8Array(request.blobAsText.length);
for (var i=0; i<bytes.length; i++) {
bytes[i] = request.blobAsText.charCodeAt(i);
}
// store blob
_blobs[_chunkIndex-1] = new Blob([bytes], {type: request.mimeString});
if (_chunkIndex == request.chunks) {
// merge all blob chunks
for (j=0; j<_blobs.length; j++) {
var mergedBlob;
if (j>0) {
// append blob
mergedBlob = new Blob([mergedBlob, _blobs[j]], {type: request.mimeString});
}
else {
mergedBlob = new Blob([_blobs[j]], {type: request.mimeString});
}
}
saveBlobToFile(mergedBlob, "myImage.png", request.mimeString);
}
}
}
);
Does my app not have access to the blob because it was created on the
extension? Can anyone please shed some light?
Exactly! You may want to pass a dataUrl instead of a blob. Something like this below could work:
/* Chrome Extension */
var blobToDataURL = function(blob, cb) {
var reader = new FileReader();
reader.onload = function() {
var dataUrl = reader.result;
var base64 = dataUrl.split(',')[1];
cb(base64);
};
reader.readAsDataURL(blob);
};
blobToDataUrl(blob, function(dataUrl) {
chrome.runtime.sendMessage(APP_ID, {databUrl: dataUrl}, function() {});
});
/* Chrome App */
function dataURLtoBlob(dataURL) {
var byteString = atob(dataURL.split(',')[1]),
mimeString = dataURL.split(',')[0].split(':')[1].split(';')[0];
var ab = new ArrayBuffer(byteString.length);
var ia = new Uint8Array(ab);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
var blob = new Blob([ia], {type: mimeString});
return blob;
}
chrome.runtime.onMessageExternal.addListener(
function(request) {
var blob = dataURLtoBlob(request.dataUrl);
saveBlobToFile(blob, "screenshot.png");
});
I am extremely interested in this question, as I am trying to accomplish something similar.
these are the questions that I have found to be related:
How can a Chrome extension save many files to a user-specified directory?
Implement cross extension message passing in chrome extension and app
Does chrome.runtime support posting messages with transferable objects?
Pass File object to background.js from content script or pass createObjectURL (and keep alive after refresh)
According to Rob W, in the first link:
"Chrome's fileSystem (app) API can directly write to the user's filesystem (e.g. ~/Documents or %USERPROFILE%\Documents), specified by the user."
If you can write to a user's filesystem you should be able to read from it right?
I haven't had the opportunity to try this out, but instead of directly passing the file blob to the app, you could save the item to your downloads using the chrome extension downloads api.
Then you could retrieve it with the chrome app filesystem api to gain access to it.
Edit:
I keep reading that the filesystem the api can access is sandboxed. So I have no idea if this solution is possible. It being sandboxed and Rob W's description of "writing directly to the user's filesystem" sound like opposites to me.
Edit:
Rob W has revised his answer here: Implement cross extension message passing in chrome extension and app.
It no longer uses a shared worker, and passes file data as a string to the backend, which can turn the string back into a blob.
I'm not sure what the max length of a message is, but Rob W also mentions a solution for slicing up blobs to send them in pieces.
Edit:
I have sent 43 mbs of data without crashing my app.
That's really an intresting question. From my point of view it can be done using these techniques:
First of all you should convert your blob to arraybuffer. This can be done with FileReader, and it is async operation
Then here comes some magic of Encoding API, which is currently available on stable Chrome. So you convert your arraybuffer into string. This operation is sync
Then you can communicate with other extensions/apps using Chrome API like this. I am using this technique to promote one of my apps (new packaged app) using another famous legacy app. And due to the fact that legacy packaged apps are in fact extensions, I think everything will be okay.
I am building a web page in which I used pdf.js project of Mozilla and its working perfectly.
But I have a need to show multiple pdf on single page, which are to be placed in different divisions.
Someone supposed me to use iframes but I need to show them in div only or i can use buttons by which i can switch to other pdfs on same page
The way of switching to other pdf with button is perfect solution and it can be done by AJAX but I don't know how to implement this functionality with AJAX. Does any one can provide me way to implement it ?
Mozilla developers have implemented following code to change the pdf in viewer when user select a pdf file from choose file tool box:
window.addEventListener('change', function webViewerChange(evt) {
var files = evt.target.files;
if (!files || files.length == 0)
return;
// Read the local file into a Uint8Array.
var fileReader = new FileReader();
fileReader.onload = function webViewerChangeFileReaderOnload(evt) {
var data = evt.target.result;
var buffer = new ArrayBuffer(data.length);
var uint8Array = new Uint8Array(buffer);
for (var i = 0; i < data.length; i++)
uint8Array[i] = data.charCodeAt(i);
PDFView.load(uint8Array);
};
But i want to work this code on the button click event and it should load the pre-specified pfd on viewer.
I'm developing my own portfolio website, which is based on JavaScript gallery. The script shows and prealoads images by tracking current position and it works brilliant when it comes to load only one filetype. Here comes extract:
var $current = 1;
var $sourceImage = 'path-to-images/'+$current+'.jpg';
var $newImage = new Image();
$newImage.src = $sourceImage;
But what if in the directory there are more than one filetype, for example: 1.jpg 2.jpg 3.gif 4.png ... ? What's the best way to find extension of file that exists on server and pass it to the variable?
Thanks for any advice.
To check if a file exists with JavaScript you have to send an ajax request:
var req = this.window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
if (!req) {
throw new Error('XMLHttpRequest not supported');
}
// HEAD Results are usually shorter (faster) than GET
req.open('HEAD', url, false);
req.send(null);
if (req.status == 200) {
console.log('file exists');
}
else {
console.log('file does not exist');
}
from phpjs.
Your solutions are limited when only using Javascript. The simplest way is to have an array containing all of the file names,
var imageFiles = ["1.jpg", "2.jpg", "3.gif", "4.png"];
However, this may be undesirable if there are a large number of images.
Alternatively, you can write a page in PHP (or any language of your choice) that returns all the images in the directory as a JSON array.
["1.jpg", "2.jpg", "3.gif", "4.png"]
Then just use a framework such as jQuery to request the page; getJSON() would work nicely in this case. You can always reinvent the wheel, but I highly suggest a framework for AJAX.
I want to read a file (on the client side) and get the content in an array. It will be just one file. I have the following and it doesn't work. 'query_list' is a textarea where I want to display the content of the file.
<input type="file" id="file" name="file" enctype="multipart/form-data"/>
<script>
document.getElementById('file').addEventListener('change', readFile, false);
function readFile (evt) {
var files = evt.target.files;
var file = files[0];
var fh = fopen(file, 0);
var str = "";
document.getElementById('query_list').textContent = str;
if(fh!=-1) {
length = flength(fh);
str = fread(fh, length);
fclose(fh);
}
document.getElementById('query_list').textContent = str;
}
</script>
How should I go about it? Eventually I want to loop over the array and run some SQL queries.
If you want to read files on the client using HTML5's FileReader, you must use Firefox, Chrome or IE 10+. If that is true, the following example reads a text file on the client.
your example attempts to use fopen that I have never heard of (on the client)
http://jsfiddle.net/k3j48zmt/
document.getElementById('file').addEventListener('change', readFile, false);
function readFile (evt) {
var files = evt.target.files;
var file = files[0];
var reader = new FileReader();
reader.onload = function(event) {
console.log(event.target.result);
}
reader.readAsText(file)
}
For IE<10 support you need to look into using an ActiveX Object like ADO.Stream Scripting.FileSystemObject http://msdn.microsoft.com/en-us/library/2z9ffy99(v=vs.85).aspx but you'll run into a security problem. If you run IE allowing all ActiveX objects (for your website), it should work.
There is such thing as HTML5 File API to access local files picked by user, without uploading them anywhere.
It is quite new feature, but supported by most of modern browsers.
I strongly recommend to check out this great article to see, how you can use it.
There is one problem with this, you can't read big files (~400 MB and larger) because straight forward FileAPI functions attempting to load entire file into memory.
If you need to read big files, or search something there, or navigate by line index check my LineNavigator, which allows you to read, navigate and search in files of any size. Try it in jsFiddle! It is super easy to use:
var navigator = new FileNavigator(file);
navigator.readSomeLines(0, function linesReadHandler(err, index, lines, eof, progress) {
// Some error
if (err) return;
// Process this line bucket
for (var i = 0; i < lines.length; i++) {
var line = lines[i];
// Do something with it
}
// End of file
if (eof) return;
// Continue reading
navigator.readSomeLines(index + lines.length, linesReadHandler);
});
Well I got beat to the answer but its different:
<input type="file" id="fi" />
<button onclick="handleFile(); return false;">click</button>
function handleFile() {
var preview = document.getElementById('prv')
var file = document.getElementById('fi').files[0];
var div = document.body.appendChild(document.createElement("div"));
div.innerHTML = file.getAsText("utf-8");
}
This will work in FF 3.5 - 3.6, and that's it. FF 4 and WebKit you need to use the FileReader as mentioned by Juan Mendes.
For IE you may find a Flash solution.
I work there, but still wanted to contribute because it works well: You can use the filepicker.io read api to do exactly this. You can pass in an dom element and get the contents back, for text or binary data, even in IE8+