Taking screenshot as array discards transparency

[miek0tube]

Taking a offscreen screenshot works just fine when saving it to a file. However, when you specify "asarray" parameter, transparency information is lost:
plotter.show(
mesh,
viewup='y',
).screenshot('./_screenshot.png') # works fine saving a PNG file

img = plotter.show(
mesh,
viewup='y',
).screenshot('./_screenshot.png', ararray=True) # returns 3-channel RGB image with no tranpsarency

The cause is in file.io.py here (starting from line 1822):
if asarray:
pd = w2if.GetOutput().GetPointData()
npdata = utils.vtk2numpy(pd.GetArray("ImageScalars"))
npdata = npdata[:, [0, 1, 2]] #### ----------- DISCARDING 4th channel --------- ########
ydim, xdim, _ = w2if.GetOutput().GetDimensions()
npdata = npdata.reshape([xdim, ydim, -1])
npdata = np.flip(npdata, axis=0)
return npdata
When the marked line is removed, everything works as supposed to.