GalleryButton, GalleryPage: Cache images
Currently, the gallery button draws a scaled thumbnail of the full image on every redraw. Since it's animated, this means we're scaling a full size image every frame.
Instead, as suggested in this thread, the already-shrunk thumbnail should be cached.
The same goes for the gallery page, which also needs to scale images.
Don't forget about the scale factor when creating the cached image.
Edited by James Westman