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qtopengltextures

How to use compressed / encoded textures in QML?

Is it possible to send to a QImage data from a compressed texture directly in qml?

Right now I'm having the following code :

Image 
{
  anchors.fill: parent
  fillMode : Image.Stretch
  source : "Textures/BG_png.png"
}

Then, I create images having sources with various formats , more precisely :

// uncompressed
source : "Textures/BG_RGB565.dds"
source : "Textures/BG_RGB888.dds"
source : "Textures/BG_RGBA8888.dds"

//compressed
source : "Textures/BG_ETC1.ktx"
source : "Textures/BG_ETC1.pkm"
source : "Textures/BG_ETC1.dds"
source : "Textures/BG_PVR.pvr"
source : "Textures/BG_ASTC.astc"

I'm getting the following error "QML Image : invalid image data" for every source type except BG_RGB565.dds (and only with the ".dds" extension).

I the following questions :

  1. why does RGB565.dds work and RGB888 or other uncompressed formats don't ?

  2. what OpenGL image types do QT QML support, and how do you hint the Image class that it's source is encoded / compressed in a certain way using QML only ?

Solution

  • You'll have to implement this yourself using a QQuickImageProvider.

    Set the QQuickImageProvider's type to:

    QQmlImageProviderBase::Texture

    Then return a QSGTextureProvider from requestTexture(const QString &id, QSize *size, const QSize &requestedSize)

    See more details here: https://doc.qt.io/qt-5/qquickimageprovider.html

    Currently the only supported formats that Image {} supports is: https://doc.qt.io/qt-5/qtimageformats-index.html

    It might be possible to load it from Qt3D, but I'm not sure if these formats are supported.