Why is Illustrator's minus front not working?

I have some white lines (converted to path) on top of my star shape (rasterized) as shown in the picture. I am trying to "delete" the white lines from the shape so the shape gaps can be seen in transparent if that makes sense. The rectangle on top right shows what I am trying to achieve.

I tried to select both the star and the lines path and use Minus Front from Pathfinder and although there seems to accept the command nothing happens. What am I doing wrong? Can this also be achieved using clipping masks?