TAdvSmoothTabPage picture on tab transparent

setting does not work with image - transparent=true:

TAdvSmoothTabPage.TabAppearance.Picture.Transparent := True

What picture type do you use? Is this a bitmap?

yes, picture is bitmap from TImageList

I checked this and TAdvSmoothTabPage uses GDI+ to draw the picture on the tab. This means that for having a transparent image, you'd need to use an image format that supports transparency. This is for example a GIF or PNG with transparency. If you use a bitmap, it needs to be a bitmap with a 32bit encoding with an alpha channel.

I tried different types of images, but it always remains white space around the image on the image size. If the image is not transparent, then the background color of the image is black.

This is correct, the image needs the transparency already included, if the image is not transparent, the image will not be drawn with transparency. 

Kind Regards,