[vtkusers] Saving image with transparent background from Qt

[Ben Boeckel]

On Wed, Mar 07, 2018 at 09:45:32 +0100, Ignacio Fernández Galván via vtkusers wrote:
> Thanks, it's good to know at least I'm not doing something wrong. It 
> seems, though, that ParaView is using a custom class 
> vtkImageTransparencyFilter, so I'd have to reimplement it for plain VTK 
> (note that I'm using python, so it's not just a matter of copying the 
> cxx file).

Looking at the history, it seems that the vtkImageTransparencyFilter was
factored out of my original code in this commit:

    https://gitlab.kitware.com/paraview/paraview/commit/1eb879b95b004d3519cb24b95b95478c36d3afb4

so I imagine the fact that it's in ParaView is just for convenience. I
don't see any issue with moving the implementation to VTK. I'm not sure
which module is best for it though.

--Ben