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QPixmap change color every second

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  • J jrachman

    Hi mrjj,

    Well I am not too familiar with this framework to answer you question but you seem right. I would like those 3 rectangles to change color whether it is drawing over the rectangle or changing the color of the pixels. Either way, they seem like they achieve my goal just in different ways.

    mrjjM Offline
    mrjjM Offline
    mrjj
    Lifetime Qt Champion
    wrote on last edited by
    #4

    @jrachman
    Yes and if small images, im not sure it matter much which you use.

    J 1 Reply Last reply
    0
    • J Offline
      J Offline
      jrachman
      wrote on last edited by
      #5
      This post is deleted!
      1 Reply Last reply
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      • mrjjM mrjj

        @jrachman
        Yes and if small images, im not sure it matter much which you use.

        J Offline
        J Offline
        jrachman
        wrote on last edited by
        #6

        @mrjj Ok, would you be able to provide me with a coding example or maybe edit one of the rectangles in my project?

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

          Hi,

          QPixmap pixmap(100, 100);
          pixmap.fill(Qt::red);
          

          There you have a 100 by 100 red pixmap.

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

          J 1 Reply Last reply
          1
          • J jrachman

            @mrjj Ok, would you be able to provide me with a coding example or maybe edit one of the rectangles in my project?

            mrjjM Offline
            mrjjM Offline
            mrjj
            Lifetime Qt Champion
            wrote on last edited by
            #8

            Hi
            do you mean you want to have a widget that flashes in red,green and yellow over and over?
            like a led/lamp in some device ?

            J 1 Reply Last reply
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            • mrjjM mrjj

              Hi
              do you mean you want to have a widget that flashes in red,green and yellow over and over?
              like a led/lamp in some device ?

              J Offline
              J Offline
              jrachman
              wrote on last edited by
              #9

              @mrjj Ya like have the widget change colors every second.

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              • SGaistS SGaist

                Hi,

                QPixmap pixmap(100, 100);
                pixmap.fill(Qt::red);
                

                There you have a 100 by 100 red pixmap.

                J Offline
                J Offline
                jrachman
                wrote on last edited by
                #10

                @SGaist How would I change the color every second?

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                • SGaistS Offline
                  SGaistS Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #11

                  Using a QTimer and in the slot you update whatever widget you want to update. Since you're using a QPixmap, I guess you set it on a QLabel.

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

                  J 2 Replies Last reply
                  1
                  • SGaistS SGaist

                    Using a QTimer and in the slot you update whatever widget you want to update. Since you're using a QPixmap, I guess you set it on a QLabel.

                    J Offline
                    J Offline
                    jrachman
                    wrote on last edited by
                    #12

                    @SGaist So make an update function?

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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #13

                      That method already exists for the widgets. Again, if you are using a QLabel to show the pixmap, then you can just set the new pixmap on the label.

                      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
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                      • SGaistS SGaist

                        Using a QTimer and in the slot you update whatever widget you want to update. Since you're using a QPixmap, I guess you set it on a QLabel.

                        J Offline
                        J Offline
                        jrachman
                        wrote on last edited by jrachman
                        #14

                        @SGaist Ok and what if I want the colors to change after a specific condition. For example, for int x, x<100, and x++, change the color to green if x%2==0 (else change color to red) then wait 5 seconds. @mrjj

                        mrjjM J.HilkJ 2 Replies Last reply
                        0
                        • J jrachman

                          @SGaist Ok and what if I want the colors to change after a specific condition. For example, for int x, x<100, and x++, change the color to green if x%2==0 (else change color to red) then wait 5 seconds. @mrjj

                          mrjjM Offline
                          mrjjM Offline
                          mrjj
                          Lifetime Qt Champion
                          wrote on last edited by
                          #15

                          @jrachman
                          Hi
                          You can do all that in QTimers slot.
                          Say it calls your function every second.
                          You can then do something else after x seconds or keep track of
                          how many seconds passed since last time.

                          Do you need more than one of these "leds" in such case it would be easier to handle with a custom widget
                          as the housekeeping info would else have to live in mainwindow and could be messy for
                          more than a few flashing leds.

                          J 1 Reply Last reply
                          1
                          • J jrachman

                            @SGaist Ok and what if I want the colors to change after a specific condition. For example, for int x, x<100, and x++, change the color to green if x%2==0 (else change color to red) then wait 5 seconds. @mrjj

                            J.HilkJ Offline
                            J.HilkJ Offline
                            J.Hilk
                            Moderators
                            wrote on last edited by
                            #16

                            Hi @jrachman

                            if I may suggest a different approach.

                            For me it seems, you should subclass QWidget, and overwrite the QWidget::paintEvent function.

                            Than you can use QPainter and draw directly on the Widget

                            something like:

                            void MyWidget::paintEvent(QPaintEvent *event)
                            {
                                QWdiget::paintEvent(event);
                                QPainter painter(this);
                                painter.setRenderHint(QPainter::Antialiasing);
                                QRect rect = QRect(290, 20, 70, 40);
                                painter.fillRect(rect, Qt::red);
                            }
                            

                            Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                            Q: What's that?
                            A: It's blue light.
                            Q: What does it do?
                            A: It turns blue.

                            J 1 Reply Last reply
                            1
                            • mrjjM mrjj

                              @jrachman
                              Hi
                              You can do all that in QTimers slot.
                              Say it calls your function every second.
                              You can then do something else after x seconds or keep track of
                              how many seconds passed since last time.

                              Do you need more than one of these "leds" in such case it would be easier to handle with a custom widget
                              as the housekeeping info would else have to live in mainwindow and could be messy for
                              more than a few flashing leds.

                              J Offline
                              J Offline
                              jrachman
                              wrote on last edited by
                              #17

                              @mrjj Hmmm... ya I am not too familiar with the QTimers slot stuff and how to make that work.

                              1 Reply Last reply
                              0
                              • J.HilkJ J.Hilk

                                Hi @jrachman

                                if I may suggest a different approach.

                                For me it seems, you should subclass QWidget, and overwrite the QWidget::paintEvent function.

                                Than you can use QPainter and draw directly on the Widget

                                something like:

                                void MyWidget::paintEvent(QPaintEvent *event)
                                {
                                    QWdiget::paintEvent(event);
                                    QPainter painter(this);
                                    painter.setRenderHint(QPainter::Antialiasing);
                                    QRect rect = QRect(290, 20, 70, 40);
                                    painter.fillRect(rect, Qt::red);
                                }
                                
                                J Offline
                                J Offline
                                jrachman
                                wrote on last edited by
                                #18

                                @J.Hilk Ok I see. So would you be able to show me how you would implement this in with this example?: for int x, x<100, and x++, change the color to green if x%2==0 (else change color to red) then wait 5 seconds.

                                1 Reply Last reply
                                0
                                • SGaistS Offline
                                  SGaistS Offline
                                  SGaist
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #19

                                  You should then start by familiarising yourself with the Signals & Slots which is one of Qt's core feature.

                                  As for your use case, you could also take advantage of QObject::startTimer which would avoid using signals and slots.

                                  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
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