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QGraphicsScene Composition modes

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qt c++compositionmodeqpainter
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  • S Offline
    S Offline
    StudentScripter
    wrote on 14 Jan 2025, 20:16 last edited by
    #1

    I want to paint a black rect all over the graphicsscene, add some white holes and set the composition mode in that way that the more white a array is the more transparent it gets, showing the contents below. Whats the best way to do this?

    I tried qpainter in draw foreground with multiply on my graphicsscene, but this won't show the items below. Adding a new qgraphicsitem and doing this in its paint statement hasn't worked neither. Am i missing some flags or something?

    Appreciate any hints. :)

    P 1 Reply Last reply 15 Jan 2025, 11:04
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    • S StudentScripter
      14 Jan 2025, 20:16

      I want to paint a black rect all over the graphicsscene, add some white holes and set the composition mode in that way that the more white a array is the more transparent it gets, showing the contents below. Whats the best way to do this?

      I tried qpainter in draw foreground with multiply on my graphicsscene, but this won't show the items below. Adding a new qgraphicsitem and doing this in its paint statement hasn't worked neither. Am i missing some flags or something?

      Appreciate any hints. :)

      P Offline
      P Offline
      Pl45m4
      wrote on 15 Jan 2025, 11:04 last edited by Pl45m4
      #2

      @StudentScripter

      Have you already tried the Composition Mode Example or the Image Composition Example?

      Am i missing some flags or something

      QPainter::CompositionMode?!

      • https://doc.qt.io/qt-6/qpainter.html#CompositionMode-enum

      If debugging is the process of removing software bugs, then programming must be the process of putting them in.

      ~E. W. Dijkstra

      S 1 Reply Last reply 15 Jan 2025, 15:42
      1
      • P Pl45m4
        15 Jan 2025, 11:04

        @StudentScripter

        Have you already tried the Composition Mode Example or the Image Composition Example?

        Am i missing some flags or something

        QPainter::CompositionMode?!

        • https://doc.qt.io/qt-6/qpainter.html#CompositionMode-enum
        S Offline
        S Offline
        StudentScripter
        wrote on 15 Jan 2025, 15:42 last edited by
        #3

        @Pl45m4 Yeah forgot to set opacity to something else than 1, that solved it...

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        • S StudentScripter has marked this topic as solved on 15 Jan 2025, 15:42

        1/3

        14 Jan 2025, 20:16

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