Alpha Channel on Images

Hi. I apologise if this has been asked before.

I have a jpg background to my pages (done through: Format->Page->Background->Graphic).

I want to be able to include pictures in the document but with an alpha channel.

For example:
*I have a background of a green grass texture and want to insert a picture of a soccer ball.
*The image of the soccer ball is simply the round ball with a transparency background. (png with alpha channel trans)
*What I want when I insert the picture is for the grass page background to show around the ball. However, instead of keeping the transparency it places it in my document with a white background to the ball.
*So now, instead of a round ball on the green grass page background, I have a ball inside a white square on the grass background.

Does libreoffice not support transparency in inserted images or am I missing an important step?

EDIT: Just using: INSERT->IMAGE->FROM FILE works perfectly provided there is an alpha channel transparency in the png image. Did not try other formats.

So what is your problem? How did you insert the image, when you got the white background?