Here’s a slick-looking highlighting effect to add to your app:
Implement “Focus Area” Special Effect in iPhone Apps
…there is a light blue box in the center, which is the “focus area”. The level (represented by a Penguin) inside the focus area is the chosen level. The trick is, when you slide the levels, the penguins move in and out the focus area; and when they are outside, they turn gray; when they are inside the box, they stay as colored image. When they are on the edge, they are actually half-colored, half-gray! Isn’t that cool?
Why, that’s so cool, it superconducts. Definitely just the thing to give a scrolling selection a little stylishness!
And all done with standard UIKit, no tricky OpenGL stuff, or stacks of prerendered graphics — simply drawing images into greyscale on the fly. Although there’s enough little tricksy bits that “simply” is a bit of a misnomer. Sample project here to take a look at; reputedly acceptably smooth even on an iPhone 2G.