How to copy an Image with OpenGLImageType()?

**YetAnotherGuy** · May 15, 2019, 7:51pm

Hi guys,

I’m probably forgetting something obvious, but when I try to copy an Image with OpenGLImageType() I’m hitting an assert. Of course I’m calling both functions from within a render loop, so there should be an active context. The problem happens whether I call it from OpenGLRenderer::newOpenGLContextCreated () or from OpenGLRenderer::renderOpenGL ()

outputImage = Image(Image::PixelFormat::ARGB, currentComponent->getWidth(), currentComponent->getHeight(), true, OpenGLImageType());
Image test = outputImage.createCopy() //try to copy the Image

The assert I’m hitting. JUCE Assertion failure in juce_OpenGLGraphicsContext.cpp:221:

jassert (frameBufferID != 0); // trying to render into an uninitialised framebuffer object.

So how do I successfully create a (deep) copy of an OpenGLImageType?

**TonyAtHarrison** · May 15, 2019, 8:01pm

Looks like the initialise method for the underlying image data is not actually called if you are creating a copy:

github.com

WeAreROLI/JUCE/blob/master/modules/juce_opengl/opengl/juce_OpenGLImage.cpp#L54


}



LowLevelGraphicsContext* createLowLevelContext() override

{

    sendDataChangeMessage();

    return createOpenGLGraphicsContext (context, frameBuffer);

}



ImageType* createType() const override     { return new OpenGLImageType(); }



ImagePixelData::Ptr clone() override

{

    Image newImage (*new OpenGLFrameBufferImage (context, width, height));

    Graphics g (newImage);

    g.drawImageAt (Image (*this), 0, 0, false);



    return ImagePixelData::Ptr (newImage.getPixelData());

}



void initialiseBitmapData (Image::BitmapData& bitmapData, int x, int y, Image::BitmapData::ReadWriteMode mode) override

{

This sounds like a bug because using OpenGLImageType::create() will correctly initialise the underlying framebuffer:

github.com

WeAreROLI/JUCE/blob/master/modules/juce_opengl/opengl/juce_OpenGLImage.cpp#L192


    return 3;

}



ImagePixelData::Ptr OpenGLImageType::create (Image::PixelFormat, int width, int height, bool /*shouldClearImage*/) const

{

    OpenGLContext* currentContext = OpenGLContext::getCurrentContext();

    jassert (currentContext != nullptr); // an OpenGL image can only be created when a valid context is active!



    std::unique_ptr<OpenGLFrameBufferImage> im (new OpenGLFrameBufferImage (*currentContext, width, height));



    if (! im->initialise())

        return ImagePixelData::Ptr();



    im->frameBuffer.clear (Colours::transparentBlack);

    return *im.release();

}



OpenGLFrameBuffer* OpenGLImageType::getFrameBufferFrom (const Image& image)

{

    if (OpenGLFrameBufferImage* const glImage = dynamic_cast<OpenGLFrameBufferImage*> (image.getPixelData()))

        return &(glImage->frameBuffer);

**YetAnotherGuy** · May 16, 2019, 12:45pm

Hmm, interesting. If I use the following sequence, things do work:

outputImage = Image(Image::PixelFormat::ARGB, currentComponent->getWidth(), currentComponent->getHeight(), true, OpenGLImageType());
Image test = Image(Image::PixelFormat::ARGB, currentComponent->getWidth(), currentComponent->getHeight(), false, OpenGLImageType());
Graphics g = Graphics(test);
g.drawImage(outputImage, outputImage.getBounds().toFloat(), RectanglePlacement(), false);

Which seems to be very close to the sequence that is used internally in createCopy(), so this might indeed be a bug in JUCE itself, can anyone confirm?