Semi transparent sprite or shadow

[AcuarioCat]

Is it possible to have a semi-transparent sprite where when one sprite with transparency is on top of another sprite the transparent part causes a shadow on the sprite below but the content of the sprite below can still be seen?

[Bodmer]

The library does not have a function for that although it could be implemented with the alphaBlend function.

It is not clear whether you want to simply dim parts of a sprite (i.e. have a mask) or whether you want to overlay one image with an alpha channel on top of another image.