Are there any known size/space limitation of QPixmap and/or QImage objects documented? I did not find any useful information regarding this. I'm currently using Qt 4.7.3 on OSX and Windows. Particulary I'm interested in:
I would naively suspect that memory is the only limitation, so one could calculate max size by
width x height x byte_per_pixel
I assume that there is a more elaborate rule of thumb; also 32 bit machines may have addressing problems when you run into GB dimensions.
In the end I want to store multiple RGBA images of about 16000x16000 pixel in size and render them using transparency onto each other within a QGraphicsScene. The workstation available can have a lot of RAM, let's say 16GB.
tl;dr: What size limits of QImage/QPixmap are you aware of, or where can I find such information?
Edit: I'm aware of the tiling approach and I'm fine with that. Still it would be great to know the things described above.
Thanks!
Both are limited to 32767x32767 pixels. That is, you can think of them as using a signed 16-bit value for both the X and Y resolution.
No axis can ever exceed 32767 pixels, even if the other axis is only 1 pixel. Operating system "bitness" does not affect the limitation. The underlying system may run into other limits, such as memory as you mentioned, before such a huge image can be created.
You can see an example of this limitation in the following source code: http://git.zx2c4.com/qt/plain/src/gui/image/qpixmap_x11.cpp
if (uint(w) >= 32768 || uint(h) >= 32768) {
w = h = 0;
is_null = true;
return;
}