Hello,
I'm looking to use QSharedMemory to grab an image from a widget into
shared memory (using QWidget::grab() or QWidget::render()), so another
process/program can process the images.
So I'm looking at the QSharedMemory example here:
http://doc.qt.io/qt-5/qtcore-ipc-sharedmemory-example.html
It looks to me like the process that loads the image from the file into
shared memory has 3 deep copies. Maybe implicit sharing reduces that, I'm
not sure. But on the surface, it looks like 1) the file is loaded into a
QImage using image.load(fileName). Then 2) the QImage is streamed into a
QBuffer using out << image; And finally, 3) the buffer is memcopied into
shared memory.
So... isn't there an Qt way to do this with 1 copy? It would be trivial to
load an image from a file straight into shared memory in straight C. And
more importantly, is there a way to grab a widget image data (including
alpha channel) straight into shared memory? I'd prefer a Qt way of doing
this, but I'd also accept hacks as this doesn't need to be portable. I'm
just trying to grab a widget 30 frames a second from my Qt app and convert
it to video.
Josh
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