I am working on a project where I have to upload an image as form data along with other text fields. I have my file in Base64 string at first, then I convert it into a file before uploading it to the server.
const data = await fetch(base64String);
const blob = await data.blob();
const file = await new File([blob], 'avatar', { type: 'image/png' });
I logged the base64String in the client side before uploading it to the server. Then I upload file to the server as a File. Before saving it to MongoDB when I log it as a base64 string again in the server side, I see my string is not the same as before. I feel like while converting the base64 to file in the client side I am doing something wrong. Help me out please.
I have figured out my problem. When I take image file input from my computer I get a base64 string like below -
dataimage/jpegbase64/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAA...
But, when I convert it back into a file it expects a string like below -
/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAA....
So, basically, I had to trim the string accordingly to match the expected format and wrote a base64 to file conversion function following this answer.
Here is my function to convert a base64 string to an image file
export function getFileFromBase64(string64:string, fileName:string) {
const trimmedString = string64.replace('dataimage/jpegbase64', '');
const imageContent = atob(trimmedString);
const buffer = new ArrayBuffer(imageContent.length);
const view = new Uint8Array(buffer);
for (let n = 0; n < imageContent.length; n++) {
view[n] = imageContent.charCodeAt(n);
}
const type = 'image/jpeg';
const blob = new Blob([buffer], { type });
return new File([blob], fileName, { lastModified: new Date().getTime(), type });
}
Related
actually there are many answers for this question. But my problem is,
i want to generate pdf dynamically with 5 external(URL) images. Im using PDFmake node module.
it supports only two ways local and base64 format. But i don't want to store images locally.
so my requirement is one function which takes url as parameter and returns base64.
so that i can store in global variable and create pdfs
thanks in advance
function urlToBase(URL){
return base64;
}
var img = urlToBase('https://unsplash.com/photos/MVx3Y17umaE');
var dd = {
content: [
{
text: 'fjfajhal'
},
{
image: img,
}
]
};
var writeStream = fs.createWriteStream('myPdf.pdf');
var pdfDoc = printer.createPdfKitDocument(dd);
pdfDoc.pipe(writeStream);
pdfDoc.end();
im using PDFmake module from npm
The contents of the remote image can first be fetched with an HTTP request, for example using the ubiquitous request npm module. The image string contents can then be transformed to a buffer and finally converted to a base64 string. To complete the transformation, add the proper data-url prefix, for example, data:image/png,base64, to the beginning of the base64 string.
Here is a rough example for a PNG image:
const request = require('request-promise-native');
let jpgDataUrlPrefix = 'data:image/png;base64,';
let imageUrl = 'https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png';
request({
url: imageUrl,
method: 'GET',
encoding: null // This is actually important, or the image string will be encoded to the default encoding
})
.then(result => {
let imageBuffer = Buffer.from(result);
let imageBase64 = imageBuffer.toString('base64');
let imageDataUrl = jpgDataUrlPrefix+imageBase64;
console.log(imageDataUrl);
});
Adding CropperJS into a nodejs solution, and I'm trying to get the returned Base64 string back into file format. So I can send the file to the upload function.
I can't change any functionality and need to use file type to send as a parameter.
I tried: Creating a blob and passing it -> get an error can't to parse the file.
//this is used to upload the file
File.upload(file).then(function (savedFile) {
//with the new cropper i get back base64 string from:
$scope.imgSrc = $scope.cropperCrop.getCroppedCanvas().toDataURL();
How do I convert imgSrc to file to pass into the File upload function?
You can use this function to convert Base64 image string to image/file object.
function dataURLtoFile(dataurl, filename) {
var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],
bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
while(n--){
u8arr[n] = bstr.charCodeAt(n);
}
return new File([u8arr], filename, {type:mime});
}
//Usage example:
var base64String = "data:image/jpeg;base64,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"
var file = dataURLtoFile(base64String, 'filename.png');
console.log(file);
I'm using this, in react, to base64 encode an image file:
fileToBase64 = (filename, filepath) => {
return new Promise(resolve => {
var file = new File([filename], filepath);
var reader = new FileReader();
reader.onload = function(event) {
resolve(event.target.result);
};
reader.readAsDataURL(file);
});
};
Which gets called by this:
handleChangeFile = event => {
const { name, files } = event.target;
if (files.length) {
const file = files[0];
let fields = this.state.fields;
this.fileToBase64(file).then(result => {
fields[name].value = result;
});
fields[name].isFilled = true;
this.setState({
fields: fields
});
}
};
And the whole fields variable gets posted to a django server, no issues so far.
On the python django end:
str_encoded = request.data["file"]
str_decoded = base64.b64decode(str_encoded)
The second line returns an error that binascii.Error: Invalid base64-encoded string: length cannot be 1 more than a multiple of 4. I've googled and read that this is probably a padding issue, but I don't know how to fix it.
You will have to strip the base64 string from the prefix added by javascript.
The prefix is sth like data:{type};base64,{actual-base64-string-follows}
In php, where I had same issue, I tested if string starts with "data:" prefix and I strip it from start of string up to the position of the ; (semicolon) plus 8 characters (to catch the final ";base64,").
Then you can use python to decode the base64 string remaining as it is now a valid base64 string.
I am using an input to load an image, then converting it in the data uri format to pass it into the ngImgCrop directive to crop that image.
So far I have all of this working, but I am struggling trying to upload the cropped image which is in the data uri format using ngFlow.
I have been tried several ways with no success, has anyone been able to do this?
I am afraid I am missing something, I tried using the .addFile() method and passing in the image in the data uri format but it does not work this way.
I finally found a solution, creating a Blob and pushing it into Flow's files array worked!
This StackOverflow answer also helped, as I had to convert the image in the data uri format to binary to create the Blob (the function dataURItoBlob() did it for me).
Here's the code that did it:
function uploadImage($flow) {
if ($flow) {
// 'vm.img.cropped' is the image in data uri format to upload
var blob = dataURItoBlob(vm.img.cropped);
blob.name = 'file.png';
var file = new Flow.FlowFile($flow, blob);
$flow.files.push(file)
$flow.upload();
}
}
function dataURItoBlob(dataURI) {
var binary = atob(dataURI.split(',')[1]);
var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
var array = [];
for(var i = 0; i < binary.length; i++) {
array.push(binary.charCodeAt(i));
}
return new Blob([new Uint8Array(array)], {type: mimeString});
};
I am using a plugin jsPDF which generates PDF and saves it to local file system. Now in jsPDF.js, there is some piece of code which generates pdf data in blob format as:-
var blob = new Blob([array], {type: "application/pdf"});
and further saves the blob data to local file system. Now instead of saving I need to print the PDF using plugin node-printer.
Here is some sample code to do so
var fs = require('fs'),
var dataToPrinter;
fs.readFile('/home/ubuntu/test.pdf', function(err, data){
dataToPrinter = data;
}
var printer = require("../lib");
printer.printDirect({
data: dataToPrinter,
printer:'Deskjet_3540',
type: 'PDF',
success: function(id) {
console.log('printed with id ' + id);
},
error: function(err) {
console.error('error on printing: ' + err);
}
})
The fs.readFile() reads the PDF file and generates data in raw buffer format.
Now what I want is to convert the 'Blob' data into 'raw buffer' so that I can print the PDF.
If you are not using NodeJS then you should know that the browser does not have a Buffer class implementation and you are probably compiling your code to browser-specific environment on something like browserify. In that case you need this library that converts your blob into a Buffer class that is supposed to be as perfectly equal to a NodeJS Buffer object as possible (the implementation is at feross/buffer).
If you are using node-fetch (not OP's case) then you probably got a blob from a response object:
const fetch = require("node-fetch");
const response = await fetch("http://www.stackoverflow.com/");
const blob = await response.blob();
This blob is an internal implementation and exists only inside node-fetch or fetch-blob libraries, to convert it to a native NodeJS Buffer object you need to transform it to an arrayBuffer first:
const arrayBuffer = await blob.arrayBuffer();
const buffer = Buffer.from(arrayBuffer);
This buffer object can then be used on things such as file writes and server responses.
For me, it worked with the following:
const buffer=Buffer.from(blob,'binary');
So, this buffer can be stored in Google Cloud Storage and local disk with fs node package.
I used blob file, to send data from client to server through ddp protocol (Meteor), so, when this file arrives to server I convert it to buffer in order to store it.
var blob = new Blob([array], {type: "application/pdf"});
var arrayBuffer, uint8Array;
var fileReader = new FileReader();
fileReader.onload = function() {
arrayBuffer = this.result;
uint8Array = new Uint8Array(arrayBuffer);
var printer = require("./js/controller/lib");
printer.printDirect({
data: uint8Array,
printer:'Deskjet_3540',
type: 'PDF',
success: function(id) {
console.log('printed with id ' + id);
},
error: function(err) {
console.error('error on printing: ' + err);
}
})
};
fileReader.readAsArrayBuffer(blob);
This is the final code which worked for me. The printer accepts uint8Array encoding format.
Try:
var blob = new Blob([array], {type: "application/pdf"});
var buffer = new Buffer(blob, "binary");