Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. Pixmap from QImage is broken
Forum Updated to NodeBB v4.3 + New Features

Pixmap from QImage is broken

Scheduled Pinned Locked Moved Solved General and Desktop
littlecmspixmapimageimage display
15 Posts 5 Posters 2.4k Views 3 Watching
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • Christian EhrlicherC Offline
    Christian EhrlicherC Offline
    Christian Ehrlicher
    Lifetime Qt Champion
    wrote on last edited by
    #2

    Put your qDebug() before the return in MainWindow::colorManage() will show you the warnings. Putting them after the return statement is somewhat useless.

    Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
    Visit the Qt Academy at https://academy.qt.io/catalog

    ademmlerA 1 Reply Last reply
    1
    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #3

      Hi,

      Just in case, there are several return statement in the LittleCMS sample code, you should check all of them.

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

      ademmlerA 1 Reply Last reply
      0
      • Christian EhrlicherC Christian Ehrlicher

        Put your qDebug() before the return in MainWindow::colorManage() will show you the warnings. Putting them after the return statement is somewhat useless.

        ademmlerA Offline
        ademmlerA Offline
        ademmler
        wrote on last edited by ademmler
        #4

        @Christian-Ehrlicher thx for your hint - I have overseen this :-)

        I have done this and here is the output:
        21:12:06: Starting /Users/ademmler/QtTryouts/GraphicsViewer/build/debug/GraphicsViewer.app/Contents/MacOS/GraphicsViewer ...

        Hence no error at all. As i wrote to SGaist the final image (saved to hardest for debugging) is fine. It really seems to be an issue with
        QPixmap pixmap = QPixmap::fromImage(toDisplay);

        1 Reply Last reply
        0
        • SGaistS SGaist

          Hi,

          Just in case, there are several return statement in the LittleCMS sample code, you should check all of them.

          ademmlerA Offline
          ademmlerA Offline
          ademmler
          wrote on last edited by
          #5

          @SGaist the result from littlecms is perfectly fine. As you can see from the image saved next to the executable.
          Especially when I load this into my graphics scene the result is ok:
          QPixmap pixmap;
          pixmap.load("toDisplay.jpg");

          but if I do this:
          QPixmap pixmap = QPixmap::fromImage(toDisplay);

          the image is "distorted/broken) somehow ...

          1 Reply Last reply
          0
          • M Offline
            M Offline
            mchinand
            wrote on last edited by mchinand
            #6

            What is the format of the QImage (toDisplay->format())? Can you show exactly what you mean by 'the image is distorted/broken'.

            ademmlerA 1 Reply Last reply
            0
            • Christian EhrlicherC Offline
              Christian EhrlicherC Offline
              Christian Ehrlicher
              Lifetime Qt Champion
              wrote on last edited by Christian Ehrlicher
              #7

              When I run your program, cmsCreateMultiprofileTransform() returns a nullptr and (since I corrected the qDebug - output) get the warning 'Couldn't create color transform !' and then a QMessageBox that the image conversion failed.

              Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
              Visit the Qt Academy at https://academy.qt.io/catalog

              ademmlerA 2 Replies Last reply
              1
              • Christian EhrlicherC Christian Ehrlicher

                When I run your program, cmsCreateMultiprofileTransform() returns a nullptr and (since I corrected the qDebug - output) get the warning 'Couldn't create color transform !' and then a QMessageBox that the image conversion failed.

                ademmlerA Offline
                ademmlerA Offline
                ademmler
                wrote on last edited by ademmler
                #8

                @Christian-Ehrlicher thx for your response.

                I have corrected my code - as you mentioned - but I do not get this warning.
                I get an broken image displayed. Here is a screenshot:
                http://code.ademmler.com/gvimg01.png

                And here is what qt saved to hard disk:
                http://code.ademmler.com/toDisplay.jpg

                Note:
                I have also contacted the author of little CMS - he wrote this sample code.
                I got stuck between opinions and thoughts

                1 Reply Last reply
                0
                • M mchinand

                  What is the format of the QImage (toDisplay->format())? Can you show exactly what you mean by 'the image is distorted/broken'.

                  ademmlerA Offline
                  ademmlerA Offline
                  ademmler
                  wrote on last edited by ademmler
                  #9

                  @mchinand https://littlecms.com/blog/2020/12/09/using-lcms2-on-qt/

                  little cmd uses a different format than qt - that is what the author wrote about it.
                  I just try to create a working minimal sample ...

                  Here is what the resulting image looks like:
                  http://code.ademmler.com/gvimg01.png

                  And here is what qt saved to hard disk:
                  http://code.ademmler.com/toDisplay.jpg

                  1 Reply Last reply
                  0
                  • ademmlerA Offline
                    ademmlerA Offline
                    ademmler
                    wrote on last edited by
                    #10

                    And here is the pixmap saved to hard disk:
                    http://code.ademmler.com/qtPixmap.jpg

                    Which is also ok - hence I do not understand what's going wrong with displaying this ...

                    J.HilkJ 1 Reply Last reply
                    0
                    • ademmlerA ademmler

                      And here is the pixmap saved to hard disk:
                      http://code.ademmler.com/qtPixmap.jpg

                      Which is also ok - hence I do not understand what's going wrong with displaying this ...

                      J.HilkJ Offline
                      J.HilkJ Offline
                      J.Hilk
                      Moderators
                      wrote on last edited by
                      #11

                      @ademmler have you checked the format of toDisplay ? Image::save does take guesses if the format is missing or wrong.
                      Also you should check the return type of save, in case saving fails and you actually see the file of a previous attempt


                      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.

                      ademmlerA 2 Replies Last reply
                      0
                      • Christian EhrlicherC Christian Ehrlicher

                        When I run your program, cmsCreateMultiprofileTransform() returns a nullptr and (since I corrected the qDebug - output) get the warning 'Couldn't create color transform !' and then a QMessageBox that the image conversion failed.

                        ademmlerA Offline
                        ademmlerA Offline
                        ademmler
                        wrote on last edited by
                        #12

                        @Christian-Ehrlicher said in Pixmap from QImage is broken:

                        When I run your program, cmsCreateMultiprofileTransform() returns a nullptr and (since I corrected the qDebug - output) get the warning 'Couldn't create color transform !' and then a QMessageBox that the image conversion failed.

                        Are you working on MacOS or Windows?
                        Have you littlecms installed ? Or checked if you can use the libs I provided?

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

                          @ademmler have you checked the format of toDisplay ? Image::save does take guesses if the format is missing or wrong.
                          Also you should check the return type of save, in case saving fails and you actually see the file of a previous attempt

                          ademmlerA Offline
                          ademmlerA Offline
                          ademmler
                          wrote on last edited by
                          #13

                          @J-Hilk Gold idea - I will check.

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

                            @ademmler have you checked the format of toDisplay ? Image::save does take guesses if the format is missing or wrong.
                            Also you should check the return type of save, in case saving fails and you actually see the file of a previous attempt

                            ademmlerA Offline
                            ademmlerA Offline
                            ademmler
                            wrote on last edited by
                            #14

                            @J-Hilk

                            Here is what I see in the debugger. Looks like all "images" have content.
                            http://code.ademmler.com/debugger.png

                            Pls - where can I see the "return value type" in this window?

                            1 Reply Last reply
                            0
                            • ademmlerA Offline
                              ademmlerA Offline
                              ademmler
                              wrote on last edited by ademmler
                              #15

                              Here is the reason and solution. Thanks to Marti Maria - the author of littlecms -
                              to sort this out ...

                              This program does not work because you missed the part on
                              https://littlecms.com/blog/2020/12/09/using-lcms2-on-qt/ that says:

                              Alpha channels are supported as long as the image is not using premultiplied alpha. To get alpha channel make sure to include cmsFLAGS_COPY_ALPHA in the flags field. This is explained in LittleCMS documentation.

                              So, try: toDisplay = colorManage(sourceImage, profiles, INTENT_PERCEPTUAL, cmsFLAGS_COPY_ALPHA);*

                              This fixed the issue for me.

                              1 Reply Last reply
                              2

                              • Login

                              • Login or register to search.
                              • First post
                                Last post
                              0
                              • Categories
                              • Recent
                              • Tags
                              • Popular
                              • Users
                              • Groups
                              • Search
                              • Get Qt Extensions
                              • Unsolved