[SOLVED] QML Camera - take a Square photo

[p3c0]

@guidupas Not sure. Does it take picture of the same dimensions that you specified ?

[guidupas]

@p3c0 No. So I cant resize the resolution directly from the camera. But now I will crop the image and I am facing a now problem: how can I pass the cropped image from C++ to QML?

Thanks for the help.

[p3c0]

@guidupas AFAIK you can't directly. Use QQuickImageProvider and do cropping inside requestPixmap function and return the updated image or create you own item by subclassing QQuickPaintedItem then override paint function and draw that updated image.

[guidupas]

@p3c0 Hi. Could you help me with a little piece of code. I am facing some difficulties to implement that.

Thanks a lot.

[p3c0]

@guidupas The documentation explains the examples.
QQuickPaintedItem

• register the class
• add functions to pass the image from QML
• call update to repaint with new image

QQuickImageProvider

• No need to make a plugin for QQuickImageProvider
• Make sure the image provider class gets the updated image
• Need to reload the the Image url for updates to reflect

I think subclassing QQuickPaintedItem would be a better option.

[guidupas]

Hi @p3c0 . I am trying to implement it with QQuickImageProvider but I am not understanding why it is not working. My code is below. If you could help me.

caminhoimagens.h

#ifndef MANIPULAIMAGEM_H
#define MANIPULAIMAGEM_H

#include <QObject>
#include <QImage>
#include <QQuickImageProvider>

class manipulaImagem : public QObject, public QQuickImageProvider
{
    Q_OBJECT

    Q_PROPERTY(QString imagem READ imagem WRITE setImagem NOTIFY imagemChanged)

public:
    manipulaImagem();

    QImage requestImage(const QString &id, QSize *size, const QSize &requestedSize);

    QString imagem() const;
    void setImagem(const QString &imagem_caminho);

private:
    QString p_imagem;

signals:
    void imagemChanged();
};

#endif // MANIPULAIMAGEM_H

manipulaimagem.cpp

#include "manipulaimagem.h"

#include <QDebug>

manipulaImagem::manipulaImagem() : QQuickImageProvider(QQuickImageProvider::Image)
{

}

QImage manipulaImagem::requestImage(const QString &id, QSize *size, const QSize &requestedSize)
{
    qDebug() << p_imagem;

    QImage imagemr(p_imagem);

    return imagemr;
}

QString manipulaImagem::imagem() const
{
    return p_imagem;
}

void manipulaImagem::setImagem(const QString imagem_caminho)
{
    if (imagem_caminho != p_imagem) {
        p_imagem = imagem_caminho;
        emit imagemChanged();
    }
}

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>

#include <QtQml>

#include "manipulaxml.h"
#include "caminhoimagens.h"
#include "manipulaimagem.h"

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

    qmlRegisterType<manipulaXml>("ManipXML", 1, 0, "ManipulaXML");
    qmlRegisterType<caminhoImagens>("PathImagens", 1, 0, "CaminhoImagens");
    qmlRegisterType<manipulaImagem>("ManipImagem", 1, 0, "ManipulaImagem");

    manipulaImagem *forneceImagem = new manipulaImagem();
    QQmlApplicationEngine engine;
    engine.addImageProvider("provedorImagem", forneceImagem);
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

QML

Camera {
                id: camera

                captureMode: Camera.CaptureStillImage

                imageCapture {
                    onImageCaptured: {
                        manipulaImagem.imagem = preview.toString();

                        console.log(preview.toString());

                        previewImage.source = "image://provedorImagem/fotoPerfil"
                    }
                }
            }

            VideoOutput {
                id: viewfinder
                
                visible: true

                focus: visible

                anchors.top: parent.top

                width: parent.width
                height: parent.width

                source: camera
                
                fillMode: VideoOutput.PreserveAspectCrop
      }

Rectangle {
        id: previewRectangle

        visible: false

        anchors.fill: parent

        Image {
            id: previewImage

            fillMode: Image.PreserveAspectFit

            anchors.top: parent.top

            width: parent.width
            height: parent.width
        }
}

The response for this code is:
qml: image://camera/preview_1
""
QFSFileEngine::open: No file name specified
qrc:/CriarPerfil.qml:983:9: QML Image: Failed to get image from provider: image://provedorimagem/fotoPerfil

[p3c0]

@guidupas What does preview.toString() return ? Is it the actual image data or file name ?

[guidupas]

@p3c0 Hello!

When I use console.log it returns the same result for both options:

console.log(preview.toString());
console.log(preview);

The result is:
qml: image://camera/preview_1

But there is something wrong when I pass values to the Q_PROPERTY(QString imagem READ imagem WRITE setImagem NOTIFY imagemChanged). No matter what I pass it returns me an empty string.

manipulaImagem.imagem = "AER";
manipulaImagem.imagem = preview;
manipulaImagem.imagem = preview.toString();

All the options above returns the result:
""

But I could not find what is missing.

[p3c0]

@guidupas That is the url with image id. You can now get the imageProvider from QML engine using that url. Cast QQmlImageProviderBase to QQuickImageProvider. Then you can use requestImage to get that actual camera image from image id. Once you get this image on C++ side perform operations and return it.

[guidupas]

@p3c0 Hello!

I am trying to resolve this problem by 2 ways:

First:

QImage manipulaImagem::requestImage(const QString &id, QSize *size, const QSize &requestedSize)
{
    QUrl caminhoImagem(id);

    QString imageId = caminhoImagem.path().remove(0, 1);

    QImage imagem1(id);

    if(imagem1.isNull())
    {
        qDebug() << "Erro";
    }
    else
    {
        qDebug() << "OK";
    }

    return imagem1;
}

I call this method from QML using a image provider: previewImage.source = "image://ProvedorImagens/" + preview;
In this function using QImage imagem1(id) or QImage imagem1(imageId), both return me a NULL image.
It returns me message: QML Image: Failed to get image from provider: image://provedorimagens/image://camera/preview_1

The other way is another function:

QImage manipulaImagem::recortarFotoPerfil(const QString &imagem)
{
    QUrl caminhoImagem(imagem);
    QQmlEngine *engine = QQmlEngine::contextForObject(this)->engine();
    QQmlImageProviderBase *imageProviderBase = engine->imageProvider(caminhoImagem.host());
    QQuickImageProvider *imageProvider = static_cast<QQuickImageProvider*>(imageProviderBase);

    QSize imageSize;
    QString imageId = caminhoImagem.path().remove(0, 1);
    QImage imagem1 = imageProvider->requestImage(imageId, &imageSize, imageSize);
    imagem1 = imageProvider->requestImage(imageId, &imageSize, imageSize);

    if(imagem1.isNull())
    {
        qDebug() << "Erro";
    }
    else
    {
        qDebug() << "OK";
    }

    return imagem1;
}

This function gets the image but when I return it I receive a message:
Error: Cannot assign QImage to QUrl

I call this function directly from QML:
previewImage.source = manipulaImagem.recortarFotoPerfil(preview);

I think you told me to use something like the second way but I cannot return the image to QML.

[p3c0]

@guidupas Returning a QImage wont work where QUrl is expected. Make this Image available for the image provider that your registered and then return this image from requestImage or requestPixmap.

[guidupas]

@p3c0 Hello!

The problem is exactly that, all my attempts to make the image available for the image provider fail. I have tried using a Q_PROPERTY and a QImage member inside the class, but my provider always returns a null image when I try to access it to return.

[p3c0]

@guidupas But you already have the QImage (as per this error Error: Cannot assign QImage to QUrl in class manipulaImagem) as well as QQuickImageProvider instance. Is it not possible to send the image using this instance ?

[guidupas]

@p3c0 I thing it can be possible but I am not figuring out how. Take a look at this code and I think you will understand what I am talking about.

.h

#ifndef MANIPULAIMAGEM_H
#define MANIPULAIMAGEM_H

#include <QObject>
#include <QImage>
#include <QQuickImageProvider>
#include <QQmlEngine>
#include <QQmlContext>

class manipulaImagem : public QObject, public QQuickImageProvider
{
    Q_OBJECT

public slots:
    QString recortarFotoPerfil(const QString &imagem, QRect rectRecorte);

public:
    manipulaImagem(QObject *parent = 0);

    QImage requestImage(const QString &id, QSize *size, const QSize &requestedSize);

private:
    void alocaImagem(const QString &imagem, QRect rectRecorte);

    QImage imagemEditada;
};

#endif // MANIPULAIMAGEM_H

.cpp

#include "manipulaimagem.h"

#include <QDebug>

manipulaImagem::manipulaImagem(QObject *parent) : QQuickImageProvider(QQmlImageProviderBase::Image)
{

}

QImage manipulaImagem::requestImage(const QString &id, QSize *size, const QSize &requestedSize)
{
    if(imagemEditada.isNull())
    {
        qDebug() << "Request image: (image is null)";
    }
    else
    {
        qDebug() << "Request image: image is OK";
    }

    return imagemEditada;
}

void manipulaImagem::alocaImagem(const QString &imagem, QRect rectRecorte)
{
    QUrl caminhoImagem(imagem);
    QQmlEngine *engine = QQmlEngine::contextForObject(this)->engine();
    QQmlImageProviderBase *imageProviderBase = engine->imageProvider(caminhoImagem.host());
    QQuickImageProvider *imageProvider = static_cast<QQuickImageProvider*>(imageProviderBase);

    QSize imageSize;
    QString imageId = caminhoImagem.path().remove(0, 1);
    imagemEditada = imageProvider->requestImage(imageId, &imageSize, imageSize);

    if(imagemEditada.isNull())
    {
        qDebug() << "Loading image failed";
    }
    else
    {
        qDebug() << "Loading image OK";
    }
}

QString manipulaImagem::recortarFotoPerfil(const QString &imagem, QRect rectRecorte)
{
    this->alocaImagem(imagem, rectRecorte);

    QString a = "image://ProvedorImagens/imagemEditada";

    if(imagemEditada.isNull())
    {
        qDebug() << "Imagem is null";
    }
    else
    {
        qDebug() << "Imagem is loaded";
    }

    return a;
}

.qml

ManipulaImagem {
        id: manipulaImagem
}

Camera {
                id: camera

                captureMode: Camera.CaptureStillImage

                imageCapture {
                    onImageCaptured: {
                        previewImage.source = manipulaImagem.recortarFotoPerfil(preview, viewfinder.mapRectToSource(Qt.rect(viewfinder.x, viewfinder.y, viewfinder.width, viewfinder.height)));
                    }
                }
            }

Rectangle {
        id: previewRectangle

        visible: false

        anchors.fill: parent

        Image {
            id: previewImage

            fillMode: Image.PreserveAspectFit
            
            anchors.top: parent.top

            width: parent.width
            height: parent.width
        }
    }

Now take a look at the output:

Loading image OK
Imagem is loaded
Request image: (image is null)
QML Image: Failed to get image from provider: image://provedorimagens/imagemEditada

How you can see when I call the functions the image is not null, but when I try to return the QImage using the provider it cant return the image. I dont know why but for the image provider the image is null.

[p3c0]

@guidupas Strange.. According to the order of the execution of the code, imagemEditada should not be null when the image is requested by Image element. May be I'm too missing something.

[guidupas]

@p3c0 I found the error. I am targeting the wrong pointer. Actually I need to connect the provider pointer im main.cpp and I am creating a new pointer to the provider.

[guidupas]

@p3c0 Could you take a look at this topic? I need some help to do exactly that connection between the provider pointer with a signal that send to it the QImage.
https://forum.qt.io/topic/60383/connecting-qquickimageprovider

[p3c0]

@guidupas said:

@p3c0 I found the error. I am targeting the wrong pointer. Actually I need to connect the provider pointer im main.cpp and I am creating a new pointer to the provider.

Well then pass the right pointer ?

To use signals and slots you will need the right pointer too.

[guidupas]

@p3c0 I found the right pointer. It is in the main.cpp
Now, how can I connect a slot inside this pointer to a signal in processaImagem.cpp?
main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>

#include <QtQml>

#include "manipulaxml.h"
#include "caminhoimagens.h"
#include "manipulaimagem.h"

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

    qmlRegisterType<manipulaXml>("ManipXML", 1, 0, "ManipulaXML");
    qmlRegisterType<caminhoImagens>("PathImagens", 1, 0, "CaminhoImagens");
    qmlRegisterType<manipulaImagem>("ManipImagem", 1, 0, "ManipulaImagem");

    QQmlApplicationEngine engine;

    manipulaImagem *imageProvider = new manipulaImagem;
    engine.addImageProvider("ProvedorImagens", imageProvider);

    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

[p3c0]

@guidupas Don't register the manipulaImagem class. Instead set it as a context property too as you already have that instance.
manipulaImagem *imageProvider = new manipulaImagem
In this way you access the same instance from QML for both Image and as context property.