When resize a transparent background image, after the image resized the background changed to white.
I modified the core QControlImageBase to handle background transparency.
Here is the code:
https://github.com/snowmann/qcodo/commit/929701a93dee79b65b61ebfa37fb50ff9f79d3d5
and
https://github.com/snowmann/qcodo/commit/f12fd7ee7a3bb320c93ee1068f91659c511a7848