I thought these two pieces of code (they work in Chrome and Firefox) were supposed to do the same thing, but they behave in different ways. They send the binary contents of a file via an XmlHttpRequest object.
Direct XHR send:
xhr.send(file);
Read file and send contents via XHR:
var reader = new FileReader();
reader.onload = function(event) {
xhr.send(event.target.result);
};
reader.readAsBinaryString(file);
File bytes sent do not match between requests (in the second one, the file is larger than in the first one, and the file gets corrupted).
I need to make the second option work.
Any ideas?
I ran into a similar problem - Corruption with FileReader into FormData
The reader's result is a string; you need to convert it into an array buffer:
var result = e.target.result;
var l = result.length
var ui8a = new Uint8Array(l)
for (var i = 0; i < l; i++)
ui8a[i] = result.charCodeAt(i);
var bb = new (window.BlobBuilder || window.MozBlobBuilder || window.WebKitBlobBuilder)()
bb.append(ui8a.buffer)
xhr.send(bb.getBlob())
Related
I am trying to convert base64 data to file using javascript on asp.net, but i am getting( 0x800a01bd - JavaScript runtime error: Object doesn't support this action) error on final stage while converting blob to file at final stage.
Here is my code:
function dataBaseURLtoFile(str) {
// extract content type and base64 payload from original string
var pos = str.indexOf(';base64,');
var type = str.substring(5, pos);
var b64 = str.substr(pos + 8);
// decode base64
var imageContent = atob(b64);
// create an ArrayBuffer and a view (as unsigned 8-bit)
var buffer = new ArrayBuffer(imageContent.length);
var view = new Uint8Array(buffer);
// fill the view, using the decoded base64
for (var n = 0; n < imageContent.length; n++) {
view[n] = imageContent.charCodeAt(n);
}
// convert ArrayBuffer to Blob
var blob = new Blob([buffer], { type: type });
//convert blob to file
var file = new File([blob], "name", { type: "image/jpeg", });
return file;
}
I try to check your code and found that issue is on line below.
var file = new File([blob], "name", { type: "image/jpeg", });
IE and Edge browser does not supports the File() constructor.
File.File() constructor
For IE and Edge browser you need to use any alternative way.
You can try to refer thread below may give you some helpful information about alternative ways.
Is there an alternative for File() constructor for Safari and IE?
I'm making an XHR request. At the time of making the request, I don't know whether the URL will return an image or not, so I'm setting xhr.responseType="text"
If the response returns with a Content-Type of image/png [or any other image MIME type], I'm making another request with xhr.responseType="arraybuffer". I then use the arraybuffer that's returned to render the image:
var uInt8Array = new Uint8Array(arraybuffer);
var i = uInt8Array.length;
var binaryString = new Array(i);
while (i--) {
binaryString[i] = String.fromCharCode(uInt8Array[i]);
}
var data = binaryString.join('');
var base64 = window.btoa(data);
//use this base64 string to render the image
Is there any way I can avoid making the second request?
I tried doing this -
var buf = new ArrayBuffer(responseText.length);
var bufView = new Uint8Array(buf);
for (var i=0, i<responseText.length; i++) {
bufView[i] = responseText.charCodeAt(i);
}
return buf;
but the responseText isn't the same as the data in the first code sample, and the resultant ArrayBuffer doesn't render the image correctly.
I had the same problem with a PDF being corrupted, but the handler is generic and handles text, JSON and files.
The easiest way to solve this is to do it the other way round: Always make the request with:
xhr.responseType = "blob";
Then when you want the response as text, just convert the binary data to text:
xhr.response.text().then(text => {
// do something
});
Having binary as the default return type I can just convert that to text where needed.
Im trying to run in-browser encryption application which uses jQuery 1.10.2 and CryptoJS 3.2.1
the problem that I face starts at around 2mb files. File can be encrypted just fine, but when a data URI is created for the file it crashes the browser.
I would like a way around this to make it possible to encrypt files up-to 50mb's without browser crashing.
Here is the current snippt responsible for file saving via FileReader API
var reader = new FileReader();
if(body.hasClass('encrypt')){
// Encrypt the file!
reader.onload = function(e){
// Use the CryptoJS library and the AES cypher to encrypt the
// contents of the file, held in e.target.result, with the password
var encrypted = CryptoJS.AES.encrypt(e.target.result, password);
// The download attribute will cause the contents of the href
// attribute to be downloaded when clicked. The download attribute
// also holds the name of the file that is offered for download.
a.attr('href', 'data:application/octet-stream,' + encrypted);
a.attr('download', file.name + '.encrypted');
step(4);
};
// This will encode the contents of the file into a data-uri.
// It will trigger the onload handler above, with the result
reader.readAsDataURL(file);
}
else {
// Decrypt it!
reader.onload = function(e){
var decrypted = CryptoJS.AES.decrypt(e.target.result, password)
.toString(CryptoJS.enc.Latin1);
if(!/^data:/.test(decrypted)){
alert("Invalid pass phrase or file! Please try again.");
return false;
}
a.attr('href', decrypted);
a.attr('download', file.name.replace('.encrypted',''));
step(4);
};
reader.readAsText(file);
}
What can I change in above code to allow for larger files to be encrypted and decrypted?
Live site: droplet.so (currently capped at 1.5mb otherwise browser crash is guaranteed)
Kindly thanks in advance.
With a little research I found out that 1.99MB is the maximum the can be saved in the data url in chrome.
Your problem can be done by converting your data url to blob
You can find more information here:
Blob from DataURL?
Chrome crashes when URI is too long is here a similar post ( see second answer ).
EDIT:
Possible solution
function dataURItoBlob(dataURI) {
var byteString = atob(dataURI.split(',')[1]);
var mimeString = dataURI.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 bb = new BlobBuilder();
bb.append(ab);
return bb.getBlob(mimeString);
}
function download(dataURI) {
var blob = dataURItoBlob(dataURI);
var url = window.URL.createObjectURL(blob);
window.location.assign(url);
}
And you can use this code by calling download(dataURI).
I'm working in a little web app that generates an base64 image, I'm using blob to put it back into a file (is a .png but I haven't renamed it yet), now I'm trying to save it on my sever Any ideas or different approaches?
This is the script:
var img = document.getElementById("MyPix");
img.onclick = function() {
var image_data = atob(img.src.split(',')[1]);
var arraybuffer = new ArrayBuffer(image_data.length);
var view = new Uint8Array(arraybuffer);
for (var i=0; i<image_data.length; i++) {
view[i] = image_data.charCodeAt(i) & 0xff;
}
try {
var blob = new Blob([arraybuffer], {type: 'application/octet-stream'});
} catch (e) {
var bb = new (window.WebKitBlobBuilder || window.MozBlobBuilder);
bb.append(arraybuffer);
var blob = bb.getBlob('application/octet-stream');
}
var url = (window.webkitURL || window.URL).createObjectURL(blob);
valor = (document.getElementById("link").value = url)
location.href = valor;
};
I'm not very good with js so if you want to have a better idea visit the project clicking here its all javascript so just see source code.
you can't save to your server with just client-side JavaScript. Form the data you want to save in Javascript, then POST that to your server with a call to a page that you write that can turn POST data into a file on your filesystem, so in your case a .php file with code that looks for $_POST data and then writes that to file. After making sure it's safe, because anyone will be able to post data to that page, not just people using your webpage.
I have to create an image uploader for a future project (No flash, IE10+, FF7+ etc.) that does image resizing/converting/cropping on the clientside and not on the server.
So I made a javascript interface where the user can 'upload' their files and get resized/cropped in the browser directly, without ever contacting the server. The performance is OK, not that good, but it works.
The endresult is an array of canvas elements. The user can edit/crop the images after they got resized, so I keep them as canvas instead of converting them to jpeg. (Which would worsen the initial performance)
Now this works fine, but I don't know what's the best way to actually upload the finished canvas elements to the server now. (Using a asp.net 4 generic handler on the server)
I have tried creating a json object from all elements containing the dataurl of each canvas.
The problem is, when I got 10-40 pictures, the browser starts freezing when creating the dataurls, especially for images that are larger than 2 megabyte.
//images = array of UploadImage
for (var i = 0; i < images.length; i++) {
var data = document.getElementById('cv_' + i).toDataURL('image/jpg');
images[i].data = data.substr(data.indexOf('base64') + 7);
}
Also converting them to a json object (I am using json2.js) usually crashes my browser. (FF7)
My object
var UploadImage = function (pFileName, pName, pDescription) {
this.FileName = pFileName;
this.Name = pName;
this.Description = pDescription;
this.data = null;
}
The upload routine
//images = array of UploadImage
for (var i = 0; i < images.length; i++) {
var data = document.getElementById('cv_' + i).toDataURL('image/jpg');
images[i].data = data.substr(data.indexOf('base64') + 7);
}
var xhr, provider;
xhr = jQuery.ajaxSettings.xhr();
if (xhr.upload) {
xhr.upload.addEventListener('progress', function (e) {
console.log(Math.round((e.loaded * 100) / e.total) + '% done');
}, false);
}
provider = function () {
return xhr;
};
var ddd = JSON.stringify(images); //usually crash here
$.ajax({
type: 'POST',
url: 'upload.ashx',
xhr: provider,
dataType: 'json',
success: function (data) {
alert('ajax success: data = ' + data);
},
error: function () {
alert('ajax error');
},
data: ddd
});
What would be the best way to send the canvas elements to the server?
Should I send them all at once or one by one?
Uploading files one by one is better. Requires less memory and as soon as one file ready to upload, the upload can be started instead of waiting while all files will be prepared.
Use FormData to send files. Allows to upload files in binary format instead of base64 encoded.
var formData = new FormData;
If Firefox use canvas.mozGetAsFile('image.jpg') instead of canvas.toDataUrl(). Allow to avoid unnecessary conversion from base64 to binary.
var file = canvas.mozGetAsFile('image.jpg');
formData.append(file);
In Chrome use BlobBuilder to convert base64 into blob (see dataURItoBlob function
accepted
After playing around with a few things, I managed to figure this out myself.
First of all, this will convert a dataURI to a Blob:
//added for quick reference
function dataURItoBlob(dataURI) {
// convert base64/URLEncoded data component to raw binary data held in a string
var byteString;
if (dataURI.split(',')[0].indexOf('base64') >= 0)
byteString = atob(dataURI.split(',')[1]);
else
byteString = unescape(dataURI.split(',')[1]);
// separate out the mime component
var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
// write the bytes of the string to a typed array
var ia = new Uint8Array(byteString.length);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
return new Blob([ia], {type:mimeString});
}
From this question):
var blob = dataURItoBlob(canvas.toDataURL('image/jpg'));
formData.append(blob);
And then send the formData object. I'm not sure how to do it in jQuery, but with plain xhr object it like so:
var xhr = new XMLHttpRequest;
xhr.open('POST', 'upload.ashx', false);
xhr.send(formData);
On server you can get files from Files collection:
context.Request.Files[0].SaveAs(...);