Transparent image over lines

[Pidi]

I have a transparent image (PNG) that I want to show over lines I already created in my document.

Is that possible?
The image is a RGB file.
I read something about removing the Alpha Channel? How?

Simple example:

[IDEAL Software Support]

Transparent images are not supported. For transparent images, the background is drawn solid white. You only need to remove the alpha channel, if it is displayed with a wrong (instead of white) background color.