QML: how to upload a photo from Camera to a web server using XMLHttpRequest

[oleroux]

Hi,

I'm using Qt 5.3 to build my first QML app.
I have a Qt Quick application which takes a photo using Camera, from the QtMultimedia module.
I would like to upload this image on a web server using XMLHttpRequest, through a POST request. The API I have to use requires multi-part mime header.
How can I do that? Is it possible to build this request using QML only or do I need a bit of C++?

My image is stored in an Image type (I can display it, it works) :
@Image {
id: photo
}@

My upload function looks like this, but is incomplete at the moment:
@function uploadImage(server, callback) {
var req = new XMLHttpRequest();
req.onreadystatechange = function() {
if (req.readyState == XMLHttpRequest.HEADERS_RECEIVED) {
console.log("Debug: header: " + req.getAllResponseHeaders ());
} else if (req.readyState == XMLHttpRequest.DONE) {
console.log("Debug: xml response: " + req.responseText);
}
}

    req.open("POST", server + "/api/cAddImage");
    // here I don't know to to build the request to send 'photo'???
    req.setRequestHeader(???);
    req.send(???);
}@

Thanks in advance,
Best regards

[SGaist]

Hi and welcome to devnet,

Maybe "this":http://stackoverflow.com/questions/9713058/sending-post-data-with-a-xmlhttprequest will help

[oleroux]

Thank you for your answer.

I found this post before and it works to send text data.
E.g. , here is my code to send credentials to log on the server:

@req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
req.send("username=" + username + "&password=" + password);@

But I cannot find the right syntax to send an image???

[p3c0]

May be using FormData. Never tried though.

[oleroux]

Here is my solution: image uploading is performed by a separate C++ class, using QNetworkAccessManager:

@#ifndef IMAGEUPLOADER_H
#define IMAGEUPLOADER_H

#include <QDebug>
#include <QFile>
#include <QFileInfo>
#include <QHttpMultiPart>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QString>

class ImageUploader: public QObject {
Q_OBJECT

public:
ImageUploader(QObject* parent = 0)
: QObject (parent)
, m_networkAccessManager(NULL)
, m_networkReply (NULL) {
m_networkAccessManager = new QNetworkAccessManager(this);
}

public slots:
void uploadImage(const QString& imageFilename) {
QFileInfo fileInfo(imageFilename);
QFile* file = new QFile(imageFilename);
if (!file->open(QIODevice::ReadWrite)) {
emit imageUploaded(999, "Image not found");
return;
}

    emit imageUploaded(-1, "Try to upload image to server, please wait...");

    QHttpMultiPart* multiPart = new QHttpMultiPart(QHttpMultiPart::FormDataType);
    QHttpPart imagePart;
    imagePart.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("image/jpeg"));
    imagePart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant(QString("form-data; name=\"image\"; filename=\"%1\"").arg(fileInfo.fileName()).toLatin1()));
    imagePart.setBodyDevice(file);
    file->setParent(multiPart);
    multiPart->append(imagePart);

    QNetworkRequest request("http://www.myserver.com/uploadImage");
    m_networkReply = m_networkAccessManager->post(request, multiPart);
    multiPart->setParent(m_networkReply);

    connect(m_networkReply, SIGNAL(finished()), this, SLOT(uploadImageFinished()));

private slots:
void uploadImageFinished() {
QString xmlReply = QString(m_networkReply->readAll());
delete m_networkReply;
qDebug() << xmlReply;
// here, you can parse the reply from the server...
emit imageUploaded(0, "Image successfully uploaded");
}

signals:
// errorCode = -1 : start image uploading
// 0 : success
// >0: error
void imageUploaded(int errorCode, const QString& errorMessage);

private:
QNetworkAccessManager* m_networkAccessManager;
QNetworkReply* m_networkReply;
};

#endif // IMAGEUPLOADER_H
@

To access the "image uploader" object from QML, we need to perform the binding, for example, in the main...

@#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include "ImageUploader.h"

int main(int argc, char* argv[])
{
QApplication app(argc, argv);

QQmlApplicationEngine engine;
ImageUploader imageUploader;
engine.rootContext()->setContextProperty("imageUploader", &imageUploader);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

return app.exec();

}
@

Finally, uploadImage() method is directly used in the QML code which can also retrieve signal emitted by the C++ code. Something like that...

@import QtQuick 2.0
import QtMultimedia 5.3

Rectangle {
id: pageCapture

Connections { // to receive "imageUploaded" signal from the C++ code
    target: imageUploader 

    onImageUploaded: {
        console.log("onImageUploaded: errorCode=" + errorCode + " errorMessage=" + errorMessage);
    }
}

Camera {
    id: camera 

    imageCapture {
        onImageSaved: {
            // call the C++ method to upload image (filename is 'path')
            imageUploader.uploadImage(path);
        }
    }
}

VideoOutput {
    id: videoOutput
    source: camera
    anchors.fill: parent
    focus : visible
    fillMode: VideoOutput.PreserveAspectCrop
}    

}
@

[marcomariani111]

I can not get the code to work. Maybe the code of uploadimage.cpp is missing? Anybody can help me? Thanks in advance

[marcomariani111]

I can not get the code to work. Maybe the code of uploadimage.cpp is missing? Anybody can help me? Thanks in advance