slideshow: more efficient `bitmap`
slideshow: more efficient `bitmap`

Use bitmap with alpha, instead of with mask.

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket