The way to change webp image , below 255 transparent color?

[abobong]

XnViewMP Version 0.79 x64 (Mar 22 2016)

The way to convert a transparent image below 255 colors to webp image correctly?

The transparent color of the picture is the magenta color.
After changing, a transparent point is released, and it becomes white compulsorily.

[xnview]

you need to convert it in 32bits

[abobong]

When a picture of "below 255 colors" was converted in XNVIEWMP.
It seems that transmission image is reset.

Before contributing, a change to 32 bits is being tried already.