visually smoothing out edge of 2 columns possible?

Hi!

I want to add 2 columns to a page: the top column is a picture and the one below will have a background colour (and eventually some text). Is there a way to smooth out the end of the picture and have it fade into the background colour? Or let’s put it that way: I just want to avoid any rough edges (hence I haven’t used shape divider or can it be done with this?)

How can this be achieved? thank you very much in advance!

Martin