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QPixmap Problem

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  • C Offline
    C Offline
    Charlie_Hdz
    wrote on last edited by
    #4

    Ok, I have a program that create a .png correctly... For reference while I got the answer:

    QApplication app( argc, argv );
    
      QPixmap pixmap( 200, 200 );
      pixmap.fill( Qt::white );
    
      QPainterPath path;
    
      path.addEllipse( 80, 80, 80, 80 );
    
      path.moveTo( 120, 120 );
      path.lineTo( 120, 40 );
      path.arcTo( 40, 40, 160, 160, 90, 90 );
      path.lineTo( 120, 120 );
    
      QFont font = QApplication::font();
      font.setPixelSize( 40 );
    
      path.addText( 20, 180, font, "Path" );
    
      QPainter painter( &pixmap );
      painter.setRenderHint( QPainter::Antialiasing );
    
      painter.setPen( Qt::black );
      painter.setBrush( Qt::gray );
    
      painter.drawPath( path );
    
      pixmap.save( "path.png" );
    
      return 0;
    

    Kind Regards,
    Enrique Hernandez
    gearstech.com.mx
    chernandez@gearstech.com.mx

    O 1 Reply Last reply
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    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by SGaist
      #5

      Hi,

      You forgot to call pm.end().

      By the way since you don’t show that image you should rather use QImage as it doesn’t require a window server running.

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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      0
      • O Offline
        O Offline
        ofmrew
        wrote on last edited by
        #6

        Let me pose my question another way. What I want to do is to draw three rectangles on to something that I can save to a file in read into another application as a background, much like you see an aerial photograph overlaid with a road network. I my case, I will be digitizing the road network using the aerial photograph as a reference. I am using QPixmap, but should I be using QImage?

        1 Reply Last reply
        0
        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #7

          QPixmap is optimised for showing on screen. If you don't plan to do that then go on with QImage.

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

          1 Reply Last reply
          0
          • SGaistS SGaist

            Hi,

            You forgot to call pm.end().

            By the way since you don’t show that image you should rather use QImage as it doesn’t require a window server running.

            O Offline
            O Offline
            ofmrew
            wrote on last edited by
            #8

            @SGaist I tried pm.end with no success and I converted to QImage with no success. Linux Image Viewer still show a black image. Is Image Viewer the problem or is it something I am doing?

            1 Reply Last reply
            0
            • C Charlie_Hdz

              Ok, I have a program that create a .png correctly... For reference while I got the answer:

              QApplication app( argc, argv );
              
                QPixmap pixmap( 200, 200 );
                pixmap.fill( Qt::white );
              
                QPainterPath path;
              
                path.addEllipse( 80, 80, 80, 80 );
              
                path.moveTo( 120, 120 );
                path.lineTo( 120, 40 );
                path.arcTo( 40, 40, 160, 160, 90, 90 );
                path.lineTo( 120, 120 );
              
                QFont font = QApplication::font();
                font.setPixelSize( 40 );
              
                path.addText( 20, 180, font, "Path" );
              
                QPainter painter( &pixmap );
                painter.setRenderHint( QPainter::Antialiasing );
              
                painter.setPen( Qt::black );
                painter.setBrush( Qt::gray );
              
                painter.drawPath( path );
              
                pixmap.save( "path.png" );
              
                return 0;
              
              O Offline
              O Offline
              ofmrew
              wrote on last edited by
              #9

              @Charlie_Hdz I had to convert your program into a console application, but I got nothing. How did you creat yours, I did mine with QtCreator.
              Here is mine:
              #include <QCoreApplication>
              #include <QPainter>
              #include <QPainterPath>
              #include <QFont>
              #include <QPixmap>

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

                QPixmap pixmap( 200, 200 );
                pixmap.fill( Qt::white );
              
                QPainterPath path;
              
                path.addEllipse( 80, 80, 80, 80 );
              
                path.moveTo( 120, 120 );
                path.lineTo( 120, 40 );
                path.arcTo( 40, 40, 160, 160, 90, 90 );
                path.lineTo( 120, 120 );
              

              // QFont font = QCoreApplication::font();
              // font.setPixelSize( 40 );

              // path.addText( 20, 180, font, "Path" );

                QPainter painter( &pixmap );
                painter.setRenderHint( QPainter::Antialiasing );
              
                painter.setPen( Qt::black );
                painter.setBrush( Qt::gray );
              
                painter.drawPath( path );
              
                pixmap.save( "//home//bobwilliams//Pictures//path.png" );
              
              return a.exec();
              

              }

              C 1 Reply Last reply
              0
              • C Offline
                C Offline
                Charlie_Hdz
                wrote on last edited by
                #10

                I did a Qt Widget Application. I commented as you did and it worked. Check whether your path is correct.

                Kind Regards,
                Enrique Hernandez
                gearstech.com.mx
                chernandez@gearstech.com.mx

                1 Reply Last reply
                0
                • O Offline
                  O Offline
                  ofmrew
                  wrote on last edited by
                  #11

                  @Charlie_Hdz I change to what created the parcels.png file and got nothing. I do not see what is wrong it is very simple. I will try reducing the size and try with both QPixmap and QImage, then I will post the results.

                  In what folder did the file from pixmap.save( "path.png" ); end up.

                  C 1 Reply Last reply
                  0
                  • O ofmrew

                    @Charlie_Hdz I change to what created the parcels.png file and got nothing. I do not see what is wrong it is very simple. I will try reducing the size and try with both QPixmap and QImage, then I will post the results.

                    In what folder did the file from pixmap.save( "path.png" ); end up.

                    C Offline
                    C Offline
                    Charlie_Hdz
                    wrote on last edited by
                    #12

                    @ofmrew said in QPixmap Problem:

                    In what folder did the file from pixmap.save( "path.png" ); end up.

                    Depends, it can be saved at Home(root directory) or in the project output folder. I tried in Ubuntu.

                    Kind Regards,
                    Enrique Hernandez
                    gearstech.com.mx
                    chernandez@gearstech.com.mx

                    O 1 Reply Last reply
                    0
                    • O ofmrew

                      @Charlie_Hdz I had to convert your program into a console application, but I got nothing. How did you creat yours, I did mine with QtCreator.
                      Here is mine:
                      #include <QCoreApplication>
                      #include <QPainter>
                      #include <QPainterPath>
                      #include <QFont>
                      #include <QPixmap>

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

                        QPixmap pixmap( 200, 200 );
                        pixmap.fill( Qt::white );
                      
                        QPainterPath path;
                      
                        path.addEllipse( 80, 80, 80, 80 );
                      
                        path.moveTo( 120, 120 );
                        path.lineTo( 120, 40 );
                        path.arcTo( 40, 40, 160, 160, 90, 90 );
                        path.lineTo( 120, 120 );
                      

                      // QFont font = QCoreApplication::font();
                      // font.setPixelSize( 40 );

                      // path.addText( 20, 180, font, "Path" );

                        QPainter painter( &pixmap );
                        painter.setRenderHint( QPainter::Antialiasing );
                      
                        painter.setPen( Qt::black );
                        painter.setBrush( Qt::gray );
                      
                        painter.drawPath( path );
                      
                        pixmap.save( "//home//bobwilliams//Pictures//path.png" );
                      
                      return a.exec();
                      

                      }

                      C Offline
                      C Offline
                      Charlie_Hdz
                      wrote on last edited by
                      #13

                      @ofmrew said in QPixmap Problem:

                      I had to convert your program into a console application

                      So, hadn't have an error when QApplication header was not detected? In the console application, GUI is removed... So it causes errors.

                      Create a Qt Widget Application, then insert the code and compile. It should work in that way!

                      Kind Regards,
                      Enrique Hernandez
                      gearstech.com.mx
                      chernandez@gearstech.com.mx

                      1 Reply Last reply
                      0
                      • C Charlie_Hdz

                        @ofmrew said in QPixmap Problem:

                        In what folder did the file from pixmap.save( "path.png" ); end up.

                        Depends, it can be saved at Home(root directory) or in the project output folder. I tried in Ubuntu.

                        O Offline
                        O Offline
                        ofmrew
                        wrote on last edited by
                        #14

                        @Charlie_Hdz

                        What I meant was when you executed the code you posted, in what folder did you find the path.png file?

                        C 1 Reply Last reply
                        0
                        • SGaistS Offline
                          SGaistS Offline
                          SGaist
                          Lifetime Qt Champion
                          wrote on last edited by
                          #15

                          This one is working fine. I get a white image with several rectangles on it

                          #include <QCoreApplication>
                          #include <QFile>
                          #include <QImage>
                          #include <QPainter>
                          #include <QPointF>
                          #include <QtDebug>
                          
                          int main(int argc, char **argv)
                          {
                              QCoreApplication app(argc, argv);
                              QImage parcelMap(20000, 10000, QImage::Format_ARGB32);
                              parcelMap.fill(Qt::white);
                              QPainter pm(&parcelMap);
                              static const QPointF points1[5] = {
                              QPointF(200, 200),
                              QPointF(20000-200, 200),
                              QPointF(20000-200, 5000-100),
                              QPointF(200, 5000-100),
                              QPointF(200, 200)};
                              pm.drawPolyline(points1, 5);
                              static const QPointF points2[5] = {
                                  QPointF(200, 5000+100),
                                  QPointF(10000-100, 5000+100),
                                  QPointF(10000-100, 5000-100),
                                  QPointF(200, 5000-100),
                                  QPointF(200, 200)};
                              pm.drawPolyline(points2, 5);
                              static const QPointF points3[5] = {
                                  QPointF(10000+100, 5000+100),
                                  QPointF(20000+200, 5000+100),
                                  QPointF(20000+200, 5000-100),
                                  QPointF(10000+100, 5000-100),
                                  QPointF(10000+100, 200)};
                              pm.drawPolyline(points3, 5);
                              pm.end();
                          
                              QFile file("parcels.png");
                              if (!file.open(QIODevice::WriteOnly)) {
                                  qDebug() << "Failed to open file" << file.errorString();
                              }
                              parcelMap.save(&file, "PNG");
                              return 0;
                          

                          Interested in AI ? www.idiap.ch
                          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                          O 1 Reply Last reply
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                          • O ofmrew

                            @Charlie_Hdz

                            What I meant was when you executed the code you posted, in what folder did you find the path.png file?

                            C Offline
                            C Offline
                            Charlie_Hdz
                            wrote on last edited by
                            #16

                            @ofmrew

                            You define the output directory, in Project, Run Working Directory.

                            In this image, you can search for the "Working DIrectory"

                            0_1515184782782_Screenshot from 2018-01-05 14-38-48.png

                            Kind Regards,
                            Enrique Hernandez
                            gearstech.com.mx
                            chernandez@gearstech.com.mx

                            1 Reply Last reply
                            0
                            • SGaistS SGaist

                              This one is working fine. I get a white image with several rectangles on it

                              #include <QCoreApplication>
                              #include <QFile>
                              #include <QImage>
                              #include <QPainter>
                              #include <QPointF>
                              #include <QtDebug>
                              
                              int main(int argc, char **argv)
                              {
                                  QCoreApplication app(argc, argv);
                                  QImage parcelMap(20000, 10000, QImage::Format_ARGB32);
                                  parcelMap.fill(Qt::white);
                                  QPainter pm(&parcelMap);
                                  static const QPointF points1[5] = {
                                  QPointF(200, 200),
                                  QPointF(20000-200, 200),
                                  QPointF(20000-200, 5000-100),
                                  QPointF(200, 5000-100),
                                  QPointF(200, 200)};
                                  pm.drawPolyline(points1, 5);
                                  static const QPointF points2[5] = {
                                      QPointF(200, 5000+100),
                                      QPointF(10000-100, 5000+100),
                                      QPointF(10000-100, 5000-100),
                                      QPointF(200, 5000-100),
                                      QPointF(200, 200)};
                                  pm.drawPolyline(points2, 5);
                                  static const QPointF points3[5] = {
                                      QPointF(10000+100, 5000+100),
                                      QPointF(20000+200, 5000+100),
                                      QPointF(20000+200, 5000-100),
                                      QPointF(10000+100, 5000-100),
                                      QPointF(10000+100, 200)};
                                  pm.drawPolyline(points3, 5);
                                  pm.end();
                              
                                  QFile file("parcels.png");
                                  if (!file.open(QIODevice::WriteOnly)) {
                                      qDebug() << "Failed to open file" << file.errorString();
                                  }
                                  parcelMap.save(&file, "PNG");
                                  return 0;
                              
                              O Offline
                              O Offline
                              ofmrew
                              wrote on last edited by
                              #17

                              @SGaist Ran it and got an image of thousands of small squares. I have a screen shot, but I so not know how to post it to this message; how do I do it?

                              Also, I moved the project to windows and got a blank white image!

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                              • SGaistS Offline
                                SGaistS Offline
                                SGaist
                                Lifetime Qt Champion
                                wrote on last edited by
                                #18

                                There's an upload image button just above the editor, third from the right.

                                Interested in AI ? www.idiap.ch
                                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                • SGaistS SGaist

                                  There's an upload image button just above the editor, third from the right.

                                  O Offline
                                  O Offline
                                  ofmrew
                                  wrote on last edited by
                                  #19

                                  @SGaist I have narrowed the problem to my Mint Linux computer because I moved the one above to a Win 10 computer and I got a white rectangle with just visible rectangles. I moved the .png file to the Win 10 machine and, guess what, it showed a white rectangle with just visible rectangles. So the problem appears to be Image Viewer. Which viewer do you use on Linux computers.

                                  As for the icons on the editor, to tell the truth, I never really noticed them. Is the some documentation on their meaning and how to use them. Most are obvious, but link, picture, zen mode and the one on the end, require more explanation.

                                  Seems we spent all this time running to ground a non-problem with Qt, while the real culprit was software provided by the operating system; however, just for grins I tried GIMP Image Viewer and of course it showed the image correctly. Warning to Mint Linux users, Image Viewer is not to be trusted.

                                  Thanks to all for the help.

                                  1 Reply Last reply
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                                  • SGaistS Offline
                                    SGaistS Offline
                                    SGaist
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #20

                                    It depends on the desktop environment so there are several possible like Gwenview, Okular, etc.

                                    Zen mode simply puts the editor in full screen so you don't have any distraction and the last one on the right allows to easily insert code sample.

                                    Interested in AI ? www.idiap.ch
                                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                                    O 1 Reply Last reply
                                    1
                                    • SGaistS SGaist

                                      It depends on the desktop environment so there are several possible like Gwenview, Okular, etc.

                                      Zen mode simply puts the editor in full screen so you don't have any distraction and the last one on the right allows to easily insert code sample.

                                      O Offline
                                      O Offline
                                      ofmrew
                                      wrote on last edited by
                                      #21

                                      @SGaist Thanks. That really helps; now I can start correctly adding code and images to my posts.

                                      1 Reply Last reply
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