JPEG Image isn't displayed!?

[GodOfWar]

Hi there!
This my first time on this forum.
I'm creating an application for an exam and I need to display a JPEG image in the application.
Here is the code:

#include <QApplication>
#include <QImageReader>
#include <QWidget>
 
 class MyWidget : public QWidget
 {
 public:
     MyWidget(QWidget *parent = 0);
	 QImageReader *lettore;
 };
 
 MyWidget::MyWidget(QWidget *parent)
     : QWidget(parent)
 {
	lettore=new QImageReader("k8055.jpg");
 }
 
 int main(int argc, char *argv[])
 {
	 QApplication app(argc, argv);
     MyWidget widget;
     widget.show();
     return app.exec();
 }

#include <QApplication>
#include <QImageReader>
#include <QWidget>

 class MyWidget : public QWidget
 {
 public:
     MyWidget(QWidget *parent = 0);
	 QImageReader *lettore;
 };

 MyWidget::MyWidget(QWidget *parent)
     : QWidget(parent)
 {
	lettore=new QImageReader("k8055.jpg");
 }

 int main(int argc, char *argv[])
 {
	 QApplication app(argc, argv);
     MyWidget widget;
     widget.show();
     return app.exec();
 }

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I'm using QT 4.2.3 Open Source with Visual Studio 2005.
When I run the application I see a blank dialog with the same image size. Where is the mistake? Can you help me?

PS. Sorry for bad english but I am Italian

[marcel]

#include <QApplication>
#include <QWidget>
#include <QPixmap>
#include <QPainter>
#include <QPaintEvent>
class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
    QPixmap mPixmap;
protected:
    virtual void paintEvent( QPaintEvent* );
};
 
MyWidget::MyWidget(QWidget *parent)
 
: QWidget(parent)
{
    mPixmap = QPixmap( "k8055.jpg" );
    setFixedSize( mPixmap.size() );
}
 
 
void MyWidget::paintEvent( QPaintEvent* e )
{
    if( !mPixmap.isNull() )
    {
        QPainter painter( this );
        p.drawPixmap( 0, 0, mPixmap );
    }
}
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MyWidget widget;
    widget.show();
    return app.exec();
}

#include <QApplication>
#include <QWidget>
#include <QPixmap>
#include <QPainter>
#include <QPaintEvent>
class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
    QPixmap mPixmap;
protected:
    virtual void paintEvent( QPaintEvent* );
};

MyWidget::MyWidget(QWidget *parent)

: QWidget(parent)
{
    mPixmap = QPixmap( "k8055.jpg" );
    setFixedSize( mPixmap.size() );
}


void MyWidget::paintEvent( QPaintEvent* e )
{
    if( !mPixmap.isNull() )
    {
        QPainter painter( this );
        p.drawPixmap( 0, 0, mPixmap );
    }
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MyWidget widget;
    widget.show();
    return app.exec();
}

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[durbrak]

Try using QLabel::setPixmap().

[jpn]

Maybe you don't have JPEG support turned on? What does

qDebug() << QImageReader::supportedImageFormats();

qDebug() << QImageReader::supportedImageFormats();

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output? This requires reconfiguring and rebuilding Qt libs, see configure -help for more info.

[marcel]

Make sure the image is in the same folder as the executable. Otherwise, give the complete path when you create the QPixmap.

[elcuco]

[ot]

how are you using Qt4 OpenSource + Visual Studio?

[marcel]

The hardest part is to get Qt compiled.
To start a project, you just need to set the appropriate include paths and library paths in the project properties, just as Qt VS Integration does.

Regards

[wysota]

To start a project you just need to call "qmake -tp vc"

[marcel]

To start a project you just need to call "qmake -tp vc"

Or that...

[GodOfWar]

#include <QApplication>
#include <QWidget>
#include <QPixmap>
#include <QPainter>
#include <QPaintEvent>
class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
    QPixmap mPixmap;
protected:
    virtual void paintEvent( QPaintEvent* );
};
 
MyWidget::MyWidget(QWidget *parent)
 
: QWidget(parent)
{
    mPixmap = QPixmap( "k8055.jpg" );
    setFixedSize( mPixmap.size() );
}
 
 
void MyWidget::paintEvent( QPaintEvent* e )
{
    if( !mPixmap.isNull() )
    {
        QPainter painter( this );
        p.drawPixmap( 0, 0, mPixmap );
    }
}
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MyWidget widget;
    widget.show();
    return app.exec();
}

#include <QApplication>
#include <QWidget>
#include <QPixmap>
#include <QPainter>
#include <QPaintEvent>
class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
    QPixmap mPixmap;
protected:
    virtual void paintEvent( QPaintEvent* );
};

MyWidget::MyWidget(QWidget *parent)

: QWidget(parent)
{
    mPixmap = QPixmap( "k8055.jpg" );
    setFixedSize( mPixmap.size() );
}


void MyWidget::paintEvent( QPaintEvent* e )
{
    if( !mPixmap.isNull() )
    {
        QPainter painter( this );
        p.drawPixmap( 0, 0, mPixmap );
    }
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MyWidget widget;
    widget.show();
    return app.exec();
}

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I managed to make it work using this code thx ! (Actually I had to modify line 29).
@jpn
Where do I have to place that instruction in order to show something??

FOR ALL:
Can someone explain me why it doesn't work with the QImageReader?