Saving QCameraImageCapture as "PNG"

hamzaelazizi

Hello everyone, this is my first time ever asking someone on a forum for help (which basically means i'm deseperate), i'm also very new to Qt. So what i want to do with my application is take pictures and save them as "PNG" in a directory, when i try it everything goes well except for the format which remains "JPEG", so i've looked almost everywhere and found some interesting ways, among them is the line that starts from " QObject::connect(_image_capture, &QCameraImageCapture::imageCaptured, [=] (int id, QImage img)" but the problem when i build my project i get this error saying "no matching function for call to ‘MainWindow::connect(QScopedPointer<QCameraImageCapture>&, void (QCameraImageCapture::)(int, const QImage&), MainWindow::MainWindow(QWidget)::<lambda(int, QImage)>)’ });** ", can someone please help me out with this ? if not, how can i save the captured images in "PNG" and not "JPEG" Thank you


MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    _camera_view = new QCameraViewfinder();
    _take_image_button = new QPushButton("Take Image");
    _turn_camera_off = new QPushButton("Turn Off");
    _turn_camera_on= new QPushButton("Turn On");
    timer = new QTimer(this);

    _central_widget = new QWidget();
    setCentralWidget(_central_widget);

    _setup_ui();
    _setup_camera_devices();
    set_camera(QCameraInfo::defaultCamera());

    connect(_turn_camera_off, &QPushButton::clicked, [this]{_camera.data()->stop(); timer->stop();});
    connect(_turn_camera_on, &QPushButton::clicked, [this]{_camera.data()->start();});
    connect(timer, SIGNAL(timeout()), this, SLOT(timerfunction()));
    connect(_take_image_button, &QPushButton::clicked, [this]{
        _image_capture.data()->capture();
         timer->start(60000);
    });

  QObject::connect(_image_capture, &QCameraImageCapture::imageCaptured, [=] (int id, QImage img){
        QByteArray ba;
        QBuffer buffer(&ba);
        buffer.open(QIODevice::WriteOnly);
        img.save(&buffer, "PNG");
    });

hamzaelazizi

@JonB thank u, i think i have found the solution for this problem, here's the code :

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    _camera_view = new QCameraViewfinder();
    _take_image_button = new QPushButton("Take Image");
    _turn_camera_off = new QPushButton("Turn Off");
    _turn_camera_on= new QPushButton("Turn On");
    timer = new QTimer(this);

    _central_widget = new QWidget();
    setCentralWidget(_central_widget);

    _setup_ui();
    _setup_camera_devices();
    set_camera(QCameraInfo::defaultCamera());

    _image_capture->setCaptureDestination(QCameraImageCapture::CaptureToBuffer);

 QObject::connect(_image_capture.data(), &QCameraImageCapture::imageCaptured, [=] (int id, QImage img) {

           fileName = "image.png";
           path = QStandardPaths::writableLocation(QStandardPaths::PicturesLocation) + "/" + fileName;
           img.save(path, "PNG");
             
            });

    connect(_turn_camera_off, &QPushButton::clicked, [this]{_camera.data()->stop(); timer->stop();});
    connect(_turn_camera_on, &QPushButton::clicked, [this]{_camera.data()->start();});
    connect(timer, SIGNAL(timeout()), this, SLOT(timerfunction()));

    connect(_take_image_button, &QPushButton::clicked, [this]{
        _image_capture.data()->capture();
        });

}

VRonin

What's _image_capture what type is it?

JonB

@hamzaelazizi
You are only saving your image, as a PNG, into a (local variable) which is a QBuffer buffer, and that puts the bytes into a (local variable) which is a QByteArray ba;. I don't think your disk file (JPEG) is being altered by any code you have shown.

If you want to save it to an external file you need to do so via a QFile, or the dedicated bool QImage::save(const QString &fileName, const char *format = nullptr, int quality = -1) const.

The call you using is bool QImage::save(QIODevice *device, const char *format = nullptr, int quality = -1) const, which only writes it into memory.

hamzaelazizi

This post is deleted!

hamzaelazizi

@JonB First of all, i would like to thank u for the time u spent writing this message. Unfortunately, i don't really get how i'm going to do that ! the point is always to get to save my pictures as "PNG" and it would be even better if i could choose also where to save it ! Thank you sir !

hamzaelazizi

@VRonin in the file "mainwindow.h" _image_capture is like this :QScopedPointer<QCameraImageCapture>_image_capture;

JonB

@hamzaelazizi said in Saving QCameraImageCapture as "PNG":

if i could choose also where to save it

Well, that's exactly what you do, by specifying the filepath:

img.save("/some/path/to/a/directory/somefilename.png");

VRonin

While JonB's answer is correct there is a caveat in this case, the second argument you get here is not meant to be saved down, that is just a preview not the actual image.

What you should do is:

_image_capture->setCaptureDestination(QCameraImageCapture::CaptureToBuffer); in the constructor, to prevent saving it as a JPG
QObject::connect(_image_capture, &QCameraImageCapture::imageAvailable, [] (int id, const QVideoFrame &img){img->image().save("ImageName.png","PNG");}; to save it as a png

hamzaelazizi

@JonB thank u, i think i have found the solution for this problem, here's the code :

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    _camera_view = new QCameraViewfinder();
    _take_image_button = new QPushButton("Take Image");
    _turn_camera_off = new QPushButton("Turn Off");
    _turn_camera_on= new QPushButton("Turn On");
    timer = new QTimer(this);

    _central_widget = new QWidget();
    setCentralWidget(_central_widget);

    _setup_ui();
    _setup_camera_devices();
    set_camera(QCameraInfo::defaultCamera());

    _image_capture->setCaptureDestination(QCameraImageCapture::CaptureToBuffer);

 QObject::connect(_image_capture.data(), &QCameraImageCapture::imageCaptured, [=] (int id, QImage img) {

           fileName = "image.png";
           path = QStandardPaths::writableLocation(QStandardPaths::PicturesLocation) + "/" + fileName;
           img.save(path, "PNG");
             
            });

    connect(_turn_camera_off, &QPushButton::clicked, [this]{_camera.data()->stop(); timer->stop();});
    connect(_turn_camera_on, &QPushButton::clicked, [this]{_camera.data()->start();});
    connect(timer, SIGNAL(timeout()), this, SLOT(timerfunction()));

    connect(_take_image_button, &QPushButton::clicked, [this]{
        _image_capture.data()->capture();
        });

}

JonB

@hamzaelazizi said in Saving QCameraImageCapture as "PNG":

path = QStandardPaths::writableLocation(QStandardPaths::PicturesLocation) + "/" + fileName;

Yep, perfect! :)