I would like to upload local image file and extract text from it. I followed the below link and it works as expected when I pass URL. https://learn.microsoft.com/en-us/azure/developer/javascript/tutorial/static-web-app/add-computer-vision-react-app
I managed to configure for local image and get the base64 encoded dataURL of the uploaded image. But when I pass base64 encoded dataURL to Computer Vision API , it says "Input data is not a valid image" (POST 400 status code). I am getting error in the line that is shown below:
const analysis = await computerVisionClient.analyzeImage(urlToAnalyze, { visualFeatures });
The code I have included for handling local image:
const handleChange = (e) => {
var file = e.target.files[0];
var reader = new FileReader();
reader.onloadend = function()
{
setFileSelected(reader.result) // this is the base64 encoded dataurl
}
reader.readAsDataURL(file);
}
In computerVision.js file, I have changed the 'contentType' in header as below.
const computerVisionClient = new ComputerVisionClient(
new ApiKeyCredentials({ inHeader: {'Ocp-Apim-Subscription-Key': key, 'Content-Type': 'application/octet-stream'} }), endpoint);
I tried replacing client.read() with readTextInStream() as per docs in computerVision.js (please refer above link), but still throws error.
May I know why I get the error "Input data is not a valid image" ? Thanks.
Here is the link for input requirements.
There is a brand new online portal provided by Microsoft https://preview.vision.azure.com/demo/OCR
The advantage is that it will directly list your available resources so you just have to pick the right one, then you test, and there are also some samples.
Related
I have an issue to send the contents of a .mat file to my frontend. My end goal is to allow clients to download the content of this .mat file at the click of a button so that they end up with the same file in their possession. I use Next.js + Django Rest Framework.
My first try was as follow:
class Download(APIView):
def get(self, request):
with open('file_path.mat', 'rb') as FID:
fileInstance = FID.read()
return Response(
fileInstance,
status=200,
content_type="application/octet-stream",
)
If I print out the fileInstance element I get some binary results:
z\xe1\xfe\xc6\xc6\xd2\x1e_\xda~\xda|\xbf\xb6\x10_\x84\xb5~\xfe\x98\x1e\xdc\x0f\x1a\xee\xe7Y\x9e\xb5\xf5\x83\x9cS\xb3\xb5\xd4\xb7~XK\xaa\xe3\x9c\xed\x07v\xf59Kbn(\x91\x0e\xdb\xbb\xe8\xf5\xc3\xaa\x94Q\x9euQ\x1fx\x08\xf7\x15\x17\xac\xf4\x82\x19\x8e\xc9...
But I can't send it back to my frontend because of a
"UnicodeDecodeError: 'utf-8' codec can't decode byte 0x9c in position 137: invalid start byte"
This error is always the same regardless of which .mat file I try to send in my response.
Next I tried to use the scipy.io.loadmat() method. In this case, fileInstance gives me a much more readable dictionary object, but I still can't get it to transfer to the frontend because of the presence of NaN in my dict:
ValueError: Out of range float values are not JSON compliant
Finally, some suggested to use h5py to send back the data as such:
with h5py.File('file_path.mat', 'r') as fileInstance:
print(fileInstance)
But in that case the error I get is
Unable to open file (file signature not found)
I know my files are not corrupted because I can open them in Matlab with no problem.
With all this trouble I'm wondering if I'm using the right approach to this problem. I could technically send the dictionary obtained through 'scipy.io.loadmat()' as a str element instead of binary, but I'll have to figure out a way to convert this text back to binary inside a Javascript function. Would anybody have some ideas as to how I should proceed?
The problem was in my frontend after all. Still, here's the correct way to go about it:
class Download(APIView):
parser_classes = [FormParser, MultiPartParser]
def get(self, request):
try:
file_path = "xyz.mat"
response = FileResponse(file_path.open("rb"), content_type="application/octet-stream")
response["Content-Disposition"] = f"attachment; filename=file_name"
return response
except Exception as e:
return Response(status=500)
This should send to the frontend the right file in the right format. No need to worry about encoding and such.
Meanwhile, on the frontend you should receive the file as follows:
onClick={() => {
const url = '/url_to_your_api/';
axios({ method: 'get', url: url, responseType: 'blob' })
.then((response) => {
const { data } = response;
const fileName = 'file_name';
const blob = new Blob([data], { type: 'application/octet-stream' });
const href = URL.createObjectURL(blob);
const link = document.createElement('a');
link.href = href;
link.download = fileName + '.mat';
document.body.appendChild(link);
link.click();
document.body.removeChild(link);
URL.revokeObjectURL(href);
})
.catch((response) => {
console.error(response);
});
}}
Long story short, the part I was missing was to specify to receive the data as blob inside the 'onClick()' function. By default, responseType from Axios is set to Json/String. For that reason, my file was modified at reception and would not be usable in matlab afterwards. If you face a similar problem in the future, try to use the 'shasum' BASH function to observe the hashed value of the file. It is with the help of that function that I could deduce that my API function would return the correct value and that therefore the problem was happenign on the frontend.
I'm using React.js to create an application that would take a photo and upload it to Firebase Storage. I am using the react-webcam library, which uses this command to take a photo:
const ImageSrc = webcamRef.current.getScreenshot();
This is how I tried uploading the photo to Storage:
storage.ref(`/images`).put(imageSrc)
.on("state_changed" , alert("success") , alert)
However, the file that is uploaded is undefined (no photo).
I tried to construct an URL of the photo using blob:
const imageUrl = window.URL.createObjectURL(new Blob(webcamRef.current.getScreenshot()))
But I get this error: >Failed to construct 'Blob': The provided value cannot be converted to a sequence.
In the library it is stated that getScreenshot - Returns a base64 encoded string of the current webcam image. So, I tried to use the atob command, but I get the error: Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.
Does anyone know how I could upload the image to Firebase Storage? Any help would be appreciated!
Instead of blob, try using putString() command like this:
const task = firebase.storage().ref(`/images`).putString(imageSrc, 'data_url')
As explained in the doc, if you want to upload from a Base64url formatted string, you need to call the putString() method as follows (example from the doc):
var message = '5b6p5Y-344GX44G-44GX44Gf77yB44GK44KB44Gn44Go44GG77yB';
ref.putString(message, 'base64url').then((snapshot) => {
console.log('Uploaded a base64url string!');
});
In your case, since getScreenshot() returns a base64 encoded string, it would be something like:
const imageSrc = webcamRef.current.getScreenshot();
storage.ref(`/images`).putString(imageSrc, 'imgBase64')
.on("state_changed" , alert("success") , alert)
I'm working on AngularJS app.
Module I'm currently working on should be able to either show a preview of a spreadsheet file or allow to download it.
The steps:
When clicked on "Preview File" it should send request with needed file's name as a parameter of POST request.
Backend will find neede file, which is a .csv file, convert it to byte array type and send it to frontend.
Frontend should handle this byte array and convert it to .xls or .xlsx filetype
The spreadsheet data should be opened in some small preview read-only window, like 1000x1000 px.
The POST request line looks like that:
this.$http.post(this.url + 'endpoint/getFile', params,
{responseType: "arraybuffer", showLoadingOverlay: true}
)
The response looks indeed like ArrayBuffer: three of it in one object, i.e. Uint8Array, Uint16Array and Uint32Array.
The code which should read this and convert to content suitable for preview is not working:
const byteArray = new Uint8Array(data);
const blob = new Blob([byteArray], { type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' });
const objectUrl = URL.createObjectURL(blob);
this.$window.open(objectUrl, 'C-Sharpcorner', 'width=1000,height=1000');
Because when created the blob, it already has 0 length in bytes, so there's no data inside.
The matter of visualising the .xls in browser window, I think, can be achieved with canvas-datagrid library. Haven't used but it looks cool.
Also, I have a problem with trying to set up a mock data for node.js (and AngularMock), for local testing when there's no data on a java backend.
I'm using 'fs' and 'csv-parse':
const fs = require('fs');
const csvParse = require("csv-parse/lib/es5");
module.exports = function stir(app) {
const getFile = () => {
const csvOutput = csvParse('../static/someData.csv', (parsed) => {
return parsed;
});
fs.readFileSync(csvOutput);
};
app.post('/stir/getFile', (req, res) => res.json(getFile()));
};
Which results in error:
TypeError: path must be a string or Buffer
What is the proper way of parsing the .csv using 'csv-parse' and sending parsed data as an ArrayBuffer to frontend in Node and AngularMock?
csv-parse docs are telling that underneath, the lib will convert the parsed object to node stream.
So why that error happens?
I'm implementing file download using AngularJS and WCF. My back-end is a .NET project hosted in IIS. The file is serialized as an array of bytes and then on the client side I utilize the File API to save the content.
To simplify the problem, back-end is like:
[WebInvoke(Method = "GET", UriTemplate = "FileService?path={path}")]
[OperationContract]
public byte[] DownloadFileBaseOnPath(string path)
{
using (var memoryStream = new MemoryStream())
{
var fileStream = File.OpenRead(path);
fileStream.CopyTo(memoryStream);
fileStream.Close();
WebOperationContext.Current.OutgoingResponse.Headers["Content-Disposition"] = "attachment; filename=\"Whatever\"";
WebOperationContext.Current.OutgoingResponse.ContentType = "application/octet-stream"; // treat all files as binary file
return memoryStream.ToArray();
}
}
And on client side, it just sends a GET request to get those bytes, converts in into a blob and save it.
function sendGetReq(url, config) {
return $http.get(url, config).then(function(response) {
return response.data;
});
}
Save the file then:
function SaveFile(url) {
var downloadRequest = sendGetReq(url);
downloadRequest.then(function(data){
var aLink = document.createElement('a');
var byteArray = new Uint8Array(data);
var blob = new Blob([byteArray], { type: 'application/octet-stream'});
var downloadUrl = URL.createObjectURL(blob);
aLink.setAttribute('href', downloadUrl);
aLink.setAttribute('download', fileNameDoesNotMatter);
if (document.createEvent) {
var event = document.createEvent('MouseEvents');
event.initEvent('click', false, false);
aLink.dispatchEvent(event);
}
else {
aLink.click();
}
setTimeout(function () {
URL.revokeObjectURL(downloadUrl);
}, 1000); // cleanup
});
}
This approach works fine with small files. I could successfully download files up to 64MB. But when I try to download a file larger than 64MB, the response.body is empty in Chrome. I also used Fiddler to capture the traffic. According to Fiddler, Back-end has successfully serialized the byte array and returned it. Please refer to the screenshot below.
In this example, I was trying to download a 70MB file:
And the response.data is empty:
Any idea why this is empty for file over 70MB? Though the response itself is more than 200MB, I do have enough memory for that.
Regarding to the WCF back-end, I know I should use Stream Mode when it comes to large files. But the typical use of my application is to download files less than 10MB. So I hope to figure this out first.
Thanks
Answer my own question.
Honestly I don't know what's going wrong. The issue still persists if I transfer it as a byte array. I eventually gave up this approach by returning a stream instead. Then on the client side, adding the following configuration
{responseType : blob}
and save it as a blob.
A server side application requires authorization on file download links. This means a normal <a ng-href="{{createLinkToFile()}}"> is no longer sufficient to get enough parameters passed to the server.
When trying to use a programmatic call to the file download, I get the response data back to Dart client application. Using a simple http GET:
var url = "http://example.com/file";
headers.putIfAbsent("Authorization", () => "bearer " + token;
_http.get(url: url, headers : headers);
The future returned by the GET will hold the data, but how do I instruct the browser to download it as a file, instead of just trying to keep it in memory?
Or is there a way to just do it in a normal link?
After downloading the data from the server like shown in Using Dart to Download a PNG File (Binary File) and displaying it not working you can create a download link like shown at http://blog.butlermatt.me/2014/03/dynamically-generating-download-files/
import 'dart:html';
void main() {
List body = [ 'Some test data ...\n'];
// Create a new blob from the data.
Blob blob = new Blob(body, 'text/plain', 'native');
// Create a data:url which points to that data.
String url = Url.createObjectUrlFromBlob(blob);
// Create a link to navigate to that data and download it.
AnchorElement link = new AnchorElement()
..href = url
..download = 'random_file.txt'
..text = 'Download Now!';
// Insert the link into the DOM.
var p = querySelector('#text');
p.append(link);
}
The code of Seth solves indeed part of the problem. To make it a bit more complete, I'm now using the following:
void doPdfFileRequest(String url) {
var request = new HttpRequest();
request.open('GET', url);
request.responseType = "blob";
request.withCredentials = false;
request.setRequestHeader("Accept", _httpAcceptHeader);
request.setRequestHeader("Authorization", "bearer " + token);
request.onReadyStateChange
.listen((r) => onData(request, "filename.pdf"));
request.send();
}
void onData(HttpRequest request, String filename) {
if (request.readyState == HttpRequest.DONE && request.status == 200) {
if (!isIE()) {
var contentType = request.getResponseHeader("content-type");
AnchorElement downloadLink = new AnchorElement(
href: Url.createObjectUrlFromBlob(request.response));
downloadLink.rel = contentType;
downloadLink.download = filename;
var event = new MouseEvent("click", view: window, cancelable: false);
downloadLink.dispatchEvent(event);
} else {
var href = Url.createObjectUrlFromBlob(request.response);
window.open(href, "_self");
}
}
}
A few things to notice. Instead of using the downloadLink.click(), a mouse event is constructed to ensure that it works on Firefox as well as on Safari and Chrome. Firefox seems not to handle the click() otherwise. Binding it to the DOM as is done in the code of Seth isn't necessary.
Internet Explorer doesn't understand the download attribute, so nothing will happen, therefore a window.open is used to at least have it work (though not ideal) on IE, it's redirecting to self to avoid being hit by the pop up blocker.
There are solutions that convert the result download result to Base64 first and put it in a data:mimetype href, using the blob this isn't necessary.
A nice way to set the filename on the file to download would be through the content disposition header, but this header is marked as unsafe, so cannot be used. The filename is now set in the code.
Another note, notice that a HttpRequest is used instead http.get(), The HttpRequest allows you to set the responseType, in this case blob, which can be transformed into a object url.