Pixellate is a set of iMovie transitions that are based on our â€˜pixellateâ€™ (a.k.a. â€˜witness protectionâ€™ effect) effect. They progressively change the pixellation level during a fade. In a fade-in a heavily pixellated clip becomes less and less pixellated. In a fade-out the pixels become larger the longer the transition plays. A crossfade is simply a fade out followed by a fade-in (the crossfade does all time calculation for you).
You have control over how large the largest pixels are going to be (horizontally and vertically independently).