FreeLayers() will free all layers but it will
also draw them into the background picture. This means that
there will be no visible change after you have called
The layers will be gone but it will look as if they were still
there because they will be drawn into the background picture.
If you don't want that, set the
keep parameter to
that case, the layers will be removed and they won't be drawn
into the background. This is the same as calling RemoveLayers().
Please note: Layers will not be freed when you display a new background picture. You have to free them on your own.
You need to enable layers before you can use this function. See Layers introduction for details.