QPixmap analog in console

[timmu]

I'm writing a console application that needs to produce a graphical output. This output is two sets of values plotted against each other and a short sentence of text. I would like to use QPixmap (and QImage) for this to produce a jpeg, however, these do not work with a console application. What would be the solution? Is there some way to still use QPixmap or do I need an alternative? Thanks!

[spirit]

You should enable "gui" in your pro-file to use QPixmap/QImage.

[timmu]

Thanks! How do I enable "gui" in the pro file?

[spirit]

QT += gui

[timmu]

I'm using QPixmap and QImage with console application.
I have "QT += gui" in my *.pro file.
This is what I'm including:

#include <QApplication>
#include <QCoreApplication>
#include <QtGui>
#include <QImage>
#include <QPixmap>

#include <QApplication>
#include <QCoreApplication>
#include <QtGui>
#include <QImage>
#include <QPixmap>

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Then I add this in my code

QPixmap map(100,100);

QPixmap map(100,100);

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The code compiles fine but it terminates during runtime with this message: "segmentation fault".

It seems I don't know how to do graphics with console. This worked fine with a gui program. Any help in trouble-shooting is most apreciated.

Thanks

[spirit]

Did you rebuild you project from scratch (make clean, qmake, make) after adding QT += gui?

[timmu]

Hi Spirit.

I do:
1. "qmake -project"
2. open *.pro file and and add Qt += gui
3. (optionally "make clean")
4. qmake
5. make

[spirit]

pro

QT       += core gui
 
TARGET = console
CONFIG   += console
CONFIG   -= app_bundle
 
TEMPLATE = app
 
SOURCES += main.cpp

QT       += core gui

TARGET = console
CONFIG   += console
CONFIG   -= app_bundle

TEMPLATE = app

SOURCES += main.cpp

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main.cpp

#include <QApplication>
#include <QPixmap>
#include <QDesktopWidget>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    return QPixmap::grabWindow(a.desktop()->winId()).save("pixmap.png", "png");
//    return a.exec();
}

#include <QApplication>
#include <QPixmap>
#include <QDesktopWidget>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    return QPixmap::grabWindow(a.desktop()->winId()).save("pixmap.png", "png");
//    return a.exec();
}

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Works fine for me.

[timmu]

Thanks. I've added your lines to my *.pro file all together and one at a time but I still get the segmentation fault.

My *.pro file as it comes out of qmake -project, qmake, make:

TEMPLATE = app
TARGET = 
DEPENDPATH += .
INCLUDEPATH += .
 
# Input
HEADERS += functions.cpp
SOURCES += functions.cpp main.cpp

TEMPLATE = app
TARGET = 
DEPENDPATH += .
INCLUDEPATH += .

# Input
HEADERS += functions.cpp
SOURCES += functions.cpp main.cpp

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How to modify this correctly. Should I add QT += gui or QT += core gui?
Do I still need these:

CONFIG += console
CONFIG -= app_bundle

Thanks!

By the way in my main() I have

//I have this
QCoreApplication application(argc, argv);
//and not this
QApplication application(argc, argv);

//I have this
QCoreApplication application(argc, argv);
//and not this
QApplication application(argc, argv);

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Does this matter?

[spirit]

It would be easier if you could attach your project.

CONFIG -= app_bundle

Is only for MacOS.

CONFIG += console

Tells that your app is the console app.

[timmu]

Thanks again. I created simplified version of my project. I have 2 files .
main.cpp

#include <QApplication>
#include <QCoreApplication>
 
#include "functions.cpp"
 
#include <fstream>
#include <iostream>
#include <cstring>
#include <stdlib.h>
 
#include <QtGui>
#include <QImage>
#include <QPixmap>
#include <QDesktopWidget>
 
using namespace std;
void doPrint();
 
int main(int argc, char *argv[]) 
{
 
QCoreApplication application(argc, argv);
//QApplication application(argc, argv);
 
doPrint();
 
return 0;
}

#include <QApplication>
#include <QCoreApplication>

#include "functions.cpp"

#include <fstream>
#include <iostream>
#include <cstring>
#include <stdlib.h>

#include <QtGui>
#include <QImage>
#include <QPixmap>
#include <QDesktopWidget>

using namespace std;
void doPrint();

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

QCoreApplication application(argc, argv);
//QApplication application(argc, argv);

doPrint();

return 0;
}

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functions.cpp

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <string>
 
#include <QtGui>
#include <QImage>
#include <QPixmap>
#include <QApplication>
#include <QCoreApplication>
 
 
using namespace std;
 
 
void doPrint()
{
 
  QPixmap map(100,100);
 
  map.fill(Qt::white);
  QPainter p(&map);
  QPen pen; 
 
  p.setPen(pen);
  p.setPen(QColor(100,100,100));
  p.drawEllipse(0,0,50,50);
  p.drawLine(10,20,30,40);
 
  //map.save("figure.jpg", 0, 90);
 
cout << "Hello\n";
}

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <string>

#include <QtGui>
#include <QImage>
#include <QPixmap>
#include <QApplication>
#include <QCoreApplication>


using namespace std;


void doPrint()
{
  
  QPixmap map(100,100);

  map.fill(Qt::white);
  QPainter p(&map);
  QPen pen; 

  p.setPen(pen);
  p.setPen(QColor(100,100,100));
  p.drawEllipse(0,0,50,50);
  p.drawLine(10,20,30,40);
  
  //map.save("figure.jpg", 0, 90);

cout << "Hello\n";
}

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Do you know why this compiles but won't run? I'm using Linux. Thanks

[spirit]

This is really odd

void doPrint()
{
...
QPixmap map(100,100); exit(1);//why do you need to exit right here?
...
}

void doPrint()
{
...
QPixmap map(100,100); exit(1);//why do you need to exit right here?
...
}

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[timmu]

Sorry. I didn't really have exit(1) there. I took it out but you responded before I managed to do it. It's not really there. And it still won't run. (Please see above for correct code)

[spirit]

main should look like this

...
int main(int argc, char *argv[]) 
{
 
QApplication application(argc, argv);
 
doPrint();
 
return 0;
}

...
int main(int argc, char *argv[]) 
{

QApplication application(argc, argv);

doPrint();

return 0;
}

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Eg, QApplication must be created instead of QCoreApplication, because in this case you'll get

QPixmap: Cannot create a QPixmap when no GUI is being used

in the console.

[timmu]

Spirit, you rock! Thanks and greetings to Ukraine!

[Flass]

main should look like this

...
int main(int argc, char *argv[]) 
{
 
QApplication application(argc, argv);
 
doPrint();
 
return 0;
}

...
int main(int argc, char *argv[]) 
{

QApplication application(argc, argv);

doPrint();

return 0;
}

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Eg, QApplication must be created instead of QCoreApplication, because in this case you'll get

in the console.

thank you very much!