1. A machine readable medium storing a program for execution by at least one processing unit, the program comprising sets of instructions for: displaying a movable user-interface tool for applying either a first effect or a second effect to an image, wherein said first effect is not a direct opposite of said second effect; in response to a command to move said movable user-interface tool in a first direction, applying said first effect to said image; and in response to a command to move said user-interface tool in a second direction, applying said second effect to said image.