[Lazarus] TBitBtn image, how to make background transparent?

[Ondrej Pokorny]

On 13.05.2019 23:42, Bo Berglund via lazarus wrote:
> I have tried creating a png image (24x24 pixels) with a gray
> background equal to the shade at the bottom of the TBitBtn.
> When I assign this image as the glyph of the TBitBtn I can see the
> image square against the button since the button's gray color is
> whiting out towards the top.
> So my gray shade is not transparent...

PNG supports alpha-channel - use it.

Ondrej